------------------------------------------------------------------------------
POV-Ray Changelog Digest
------------------------------------------------------------------------------
Notes:

- As of version 3.7.0.1, this branch (`release/v3.7.0`) has been
  detached from the main POV-Ray 3.7 development, and no longer shares updates
  with it. Development of this branch is now generally limited to maintaining
  compatibility of the 3.7.0 source code with contemporary build environments.

- To view a referenced GitHub issue (#xxx), replace the leading # of the
  issue ID with the URL https://github.com/POV-Ray/povray/issues/.
  For example, to read GitHub issue #58, visit:
  https://github.com/POV-Ray/povray/issues/58

- To view a referenced flyspray bug report (FS#xxx), replace the leading
  FS# of the flyspray bug ID with the URL http://bugs.povray.org/.
  For example, to read FS#270, visit:
  http://bugs.povray.org/270

- To view a referenced newsgroup posting (<xxxxx@news.povray.org>), prefix
  the message ID with the URL http://news.povray.org/.
  The '<' and '>' are optional (if using a shell you may want to omit them).
  For example, to read <42765ef3$1@news.povray.org>, visit:
  http://news.povray.org/42765ef3$1@news.povray.org
------------------------------------------------------------------------------
Detailed changelog information is available in the file `revision.txt`, which
should be located in the same directory as this file is.
------------------------------------------------------------------------------


Changes between 3.7.0.6 and 3.7.0.7
===================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Fixed or Mitigated Bugs
-----------------------

  - Fix configure script failing to properly handle `.` directory in
    `C_INCLUDE_PATH` or `CPLUS_INCLUDE_PATH` (fixes GitHub issue #342,
    "AX_FIX_INCORRECT_PATH is broken").


Changes between 3.7.0.5 and 3.7.0.6
===================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Fixed or Mitigated Bugs
-----------------------

  - Fix configure script failing to use -lboost_system with Boost 1.66
    (fixes GitHub issue #341, "macOS build failure for 3.7.0.5").


Changes between 3.7.0.4 and 3.7.0.5
===================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Compatibility Improvements
--------------------------

  - Fixed compatibility with systems defining `NULL` as `0` when using
    `shared_ptr` from C++11 rather than boost/tr1 (GitHub issue #339).
  - Fixed compatibility with systems not exposing `atof` in the global
    namespace (reported in discussion about GitHub issue #317).
  - Eliminated use of `register` keyword to silence warnings with C++11 (where
    the keyword is deprecated) and improve compatibility with C++17 (where the
    keyword is disallowed).

Compiler Requirements
---------------------

  - To compile with Boost 1.65.0 or later, a C++11-compliant compiler will be
    required for this and any future versions of the v3.7.0 series.

Known Issues
------------

  - The 3rd party libraries bundled with the POV-Ray 3.7.0 source code have not
    been updated for C++17 compliance; as a consequence, POV-Ray for Windows
    may not compile on fully C++17-compliant compilers.


Changes between 3.7.0.3 and 3.7.0.4
===================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Fixed or Mitigated Bugs
-----------------------

  - Fixed minor error in Unix man page.
  - Fixed a bug that caused build errors when trying to compile with VS 2010
    without SP1.
  - Partially fixed incompatibility with Boost 1.65.0.

Known Issues
------------

  - To compile with Boost 1.65.0 or later, a C++11-compliant compiler is
    required.


Changes between 3.7.0.2 and 3.7.0.3
===================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Fixed or Mitigated Bugs
-----------------------

  - Updated OpenEXR file handling code to be compatible with GNU C++ compiler
    g++ 6.x (missed that code portion in 3.7.0.2).
  - Fixed a bug discovered in bicubic patch code that could theoretically lead
    to unpredictable behaviour. (To our knowledge, the official 3.7.0 Windows
    binaries should be safe.)

Other Noteworthy
----------------

  - The Windows build process is now documented in `Windows/README.md` instead
    of `Windows/README.html` and `Windows/README.txt`.


Changes between 3.7.0.1 and 3.7.0.2
===================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Fixed or Mitigated Bugs
-----------------------

  - Updated the bundled boost library to version 1.62, as the version bundled
    with the 3.7.0.1 source code (boost 1.59) turned out to have a bug that
    would have caused POV-Ray for Windows to wake the computer from sleep mode
    even when not currently rendering.
  - Updated code to be compatible with GNU C++ compiler g++ 6.x (tested with
    6.3.1).


Changes between 3.7.0 and 3.7.0.1
=================================

(Note: This version has not been released in binary form, as it does not
feature any changes in functionality over the original 3.7.0 binaries.)

This version constitutes a maintenance update of the POV-Ray 3.7.0 source
code, focused on restoring compatibility with contemporary build environments.

Compatibility Improvements
--------------------------

  - Updated the Unix build process to be compatible with modern versions of
    Automake.
  - Updated the Unix build process to automatically link the `boost_system`
    library if required, to be compatible with modern versions of the boost
    libraries.
  - Updated the source code to eliminate conflicts with C++11.
  - Updated the Unix-specific source code and build process to be compatible
    with Mac OS X.
  - Updated the bundled boost and OpenExr libraries to versions compatible with
    Microsoft Visual Studio 2015.
  - Changed the pre-compiled header files to be compatible with Microsoft
    Visual Studio 2015.

Other Noteworthy
----------------

  - Improved documentation of the Unix build process.


---------------------------------
Changes between 3.7.RC7 and 3.7.0
---------------------------------

   - This is the version 3.7.0 release, and mostly things are in order,
     however a few minor bugs have been addressed. Continued efforts towards
     addressing static code analysis issue's resulted in the inclusion of
     several high profile fixes into this release. The scene files included
     with the distribution have been reviewed as well. This includes
     version branding, deleting some older irrelevent files, and a few new
     additions. The windows version insert menu files were also updated and
     expanded. Additionally the insert menu templates are now also available
     in HTML for convenient use with 'cut and paste'. The distribution package
     has been branded with a different (AGPL3) license.

   - For technical reasons the Macintosh OS graphical user interface was not
     ready at the time of this release. However, the source code will be made
     available to users so they can build their own binary if the wish.

Windows Related:
----------------

   - moved codemax source and removed dependence on codemax header files
   - relocated cmedit source files
   - updated help file
   - updated keywords used for context-sensitive help
   - minor setup tweak
   - fix unquoted path in shell extension registration and added registry key
     backups for uninstall
   - updated source code readme.html
   - updated about box image
   - some tweaks related to console project and remove codemax project
   - removed vs8 and vs9 solutions
   - fixed issue with editor selection due to off-by-one line numbers.
     make use of SetCaretPos consistent
   - update about bitmap to remove explicit URL's and add support to about
     window code to make some areas act as hyperlinks
   - remove old 4BPP toolbar icons as 16-color mode support isn't really
     relevant anymore
   - rename a few files in bitmaps directory whose names were upper-case

Static Code Analysis:
---------------------

   - CID 967264: Non-array delete for scalars
   - CID 967298: Resource Leak
   - CID 967299: Resource Leak
   - CID 967300: Resource Leak
   - CID 967301: Resource Leak
   - CID 967302: Resource Leak
   - CID 967303: Resource Leak
   - CID 967363: Uninitialized scalar variable
   - CID 967364: Uninitialized scalar variable
   - CID 967365: Uninitialized pointer read

   - Several fixes were rolled back, pending further investigation. They have
     been tabled for inclusion in a future release.

Fixed or mitigated the following bug reports:
---------------------------------------------

   - http://bugs.povray.org/task/262  linux sources being compiled twice
   - http://bugs.povray.org/task/271  filter affects object's own brightness
   - http://bugs.povray.org/task/274  light source fading and subsurface
   - http://bugs.povray.org/task/294  splines are not thread safe
   - http://bugs.povray.org/task/304  for loop fails to perform last iteration
   - http://bugs.povray.org/task/308  heightfield computation has a regression

Other Noteworthy:
-----------------

   - assigned licences to individual source files in the distribution tree
   - minor but effective changes to octree code for improved performance
     in radiosity-heavy scenes
   - minor fix to radiosity statistics (octree samples/node)
   - cleaned up our jpeg code to use the proper constants for the jpeglib's
     custom "boolean" type (we erroneously passed standard C++ bool constants
     instead, which could lead to compile errors on some systems)
   - suppressed duplicate version message and flipped version to 3.7.0
   - moved some code (previously a temp fix) to the frontend where it belongs
   - added new include files: shapes3.inc, meshmaker.inc and makegrass.inc
   - a couple of (unix specific) developer and user contributed fixes
   - remove outdated support header files for borland, mingw and watcom
     compilers
   - add warranty disclaimer to console output
   - updates to unix man page

-----------------------------------
Changes between 3.7.RC6 and 3.7.RC7
-----------------------------------

   - This is the FINAL release candidate. It features continued refinements to
     the Windows user interface as well as the setup/install process, fixes
     found by static code analysis, and various other bug fixes.

Windows Installer:
------------------

   - POVWIN now assigns .pov file association to when installing.
   - Improved cloning of v3.6 INI and provide better defaults.
   - Various fixes/improvements to the way Windows INSTALL works and how the
     documents path is auto-detected if not specified.
   - Additional setup tweaks.

Windows Crash Reports:
----------------------

   - Fix to handle filenames with a comma in them: crash report #419.

Static Code Analysis:
---------------------

   - CID 967356: Uninitialized scalar variable
     uninit_use: Using uninitialized value "r". See also FS#267

   - CID 967224: Truncated stdio return value
     char_io: Assigning the return value of "pov_base::ITextStream::getchar()"
     to char "chr" truncated its value

   - CID 967248: Copy-paste error
     copy_paste_error: "t1" in "t1 < 1e+07." looks like a copy-paste error.
     Should it says "t2" instead

   - CID 967249  Resource leak in object
     1. alloc_new: Allocating memory by calling
        "new double[camera.Blur_Samples]"
     2. var_assign: Assigning: "this->Sample_Threshold" =
        "new double[camera.Blur_Samples]"
     3. ctor_dtor_leak: The constructor allocates field "Sample_Threshold" of
        "pov::TracePixel::FocalBlurData" but the destructor and whatever
        functions it calls do not free it

   - CID 967420: Non-virtual destructor
     Nonvirtual_dtor: Class pov::RadiosityTask::RadiosityBlockInfo has a
     destructor and a pointer to it is upcast to class pov::ViewData::BlockInfo
     which doesn't have a virtual destructor

Fixed or mitigated the following bug reports:
---------------------------------------------

   - http://bugs.povray.org/task/270  render abort-continue (+C) skips blocks
   - http://bugs.povray.org/task/267  bug in "sor" primitive causes artifacts
   - http://bugs.povray.org/task/266  improper quoted strings handling
   - http://bugs.povray.org/task/265  supress clang compilation warnings
   - http://bugs.povray.org/task/257  Input file resuming animation render
   - http://bugs.povray.org/task/249  UTF-8 files with BOM read error
   - http://bugs.povray.org/task/247  set no_radiosity in Screen_Object()
   - http://bugs.povray.org/task/238  error during #read leaves file open
   - http://bugs.povray.org/task/234  allows GD flag to work correctly
   - http://bugs.povray.org/task/233  picture index out of range
   - http://bugs.povray.org/task/232  illegal map_type usage reporting
   - http://bugs.povray.org/task/224  syntax highlighting/auto-comp (windows)
   - http://bugs.povray.org/task/153  determine I/O permission for output file
   - http://bugs.povray.org/task/150  improves POVWIN shell "open with" option
   - http://bugs.povray.org/task/135  editor tab right-click menu additions
   - http://bugs.povray.org/task/109  frame-by-frame debug data handling

Other Noteworthy:
-----------------

    - Several updates to #5678 (FS#233): workaround for fmod() apparently not
      conforming to C++ standard on some linux machines.
    - Fixed radiosity issues with "diffuse albedo" syntax.
    - Fix for benchmark thread vs CPU count (windows version).
    - Fix to get rid of a shape/poly.cpp compile warning on Linux variants
    - Added (re-enabled) crand support.
    - Couple of fixes for an issue caused by a "boost" change.
    - Build-in benchmark can now render without external distribution files.
    - Fixed a bug in file-backed image container.
    - Bump benchmark version to 2.01
    - Various windows user interface refinements
    - Added new option to prevent the system (windows) from sleeping whilst a
      render is in progress. by default this is selected.
    - Fix a long-standing bug where pressing 'pause' during a parse or render
      could sometimes put the frontend/backend sync into an unrecoverable state
    - Updated copyright information for some 3rd party libraries.
    - A few signedness fixes in image handling code.
    - Continued code cleanup including getting rid of unused code & parameters.
    - Updated VS project libraries: zlib, libpng, libjpeg
    - Added Append_File +GP option, which allows users to append streamed
      console to existing console stream output file(s).

-----------------------------------
Changes between 3.7.RC5 and 3.7.RC6
-----------------------------------

   - This release candidate features continued refinements to the Windows
     installer, VS10 code (and other) cleanup and a few bug fixes.

Windows Installer:
------------------

   - Several updates and improvements that address user feedback.
   - Fixed an issue with the XP64 installer.

Windows Source Build:
---------------------

   - Fixed ALL tiff project targets to build tiff config headers.
   - Fixed Debug/x64 target to build OpenEXR to Float.

Windows Crash Reports:
----------------------

   - Fix for divide-by-zero in stats code when radiosity query count is 0
     crash report #384, dump file #342
   - Fix merge issue from change #5387 which re-introduced a bug fixed earlier
     crash report #385, dump file #343
   - Potential fixes for a number of crash reports related to the editor
     (particularly drag&drop actions)
   - Fix for numeric overflow issues in image handling; eg: VERY large images


Fixed or mitigated the following reports:
-----------------------------------------

http://bugs.povray.org/task/241    FS#241    (Photons not working correctly)

Other Noteworthy
----------------

   - Insert menu (windows version) update from Friedrich Lohmller.
   - Fixed problems with colored transparent backgrounds.
   - Fixed the Windows help file searchable index.
   - Some general code housekeeping (comments and whitespace).
   - A minor fix for radiosity adc_bailout handling.
   - Corrected a formatting issue with radiosity statistics reporting.

-----------------------------------
Changes between 3.7.RC4 and 3.7.RC5
-----------------------------------

   - This release candidate primarily addresses the crash dump report #357
     triggered by non-closed SSLT-enabled mesh inside CSG. This fix also
     addressed several issue's with another outstanding bug report.

   - The Windows installer and crash dump submitter have been improved.

   - Changes to the post processing of the Windows help file corrected the
     broken searchable index.

   - A couple of bug reports have been addressed.

Fixed or mitigated the following reports:
-----------------------------------------

http://bugs.povray.org/task/12    FS#12    (facets pattern in normal map)
http://bugs.povray.org/task/196   FS#196   (More SSLT Caveats)
http://bugs.povray.org/task/46    FS#239   (improper uid/gid handling)

-----------------------------------
Changes between 3.7.RC3 and 3.7.RC4
-----------------------------------

   - This release candidate primarily improves upon the SSLT code, but there
     are also some other noteworthy enhancements and/or additions.

     They are listed below:

     - a keyword addition "albedo" it's a new finish attribute
     - the iridescence feature has been overhauled
     - support was added for tuning brightness of image-mapped sky spheres
     - three new tiling patterns were added

   - Building from the windows source distribution has also been simplified
   - Introduced a new windows installer
   - Added AMD optimizations for noise
   - A Windows Editor crash fix
   - Over two dozen bug reports have addressed
   - A few scene file fixes and/or additions
   - Updated the Windows help file

Subsurface Light Transport
--------------------------

  bugfixes and improvements to SSLT code;

  syntax for material definition has changed as follows:

  material {
    texture {
      pigment { PIGMENT }
      finish { ...
        subsurface { translucency COLOR }
        }
      }
    interior { ior FLOAT }
    }

  The pigment determines the SSLT material's overall appearance when applied
  to an object with sufficiently large structures. The translucency color
  (which can alternatively be a float) determines the strength of the
  subsurface light transport effect (note that the values may be >1.0; also
  note that the effect doesn't scale with the object; instead, to adjust
  materials to the dimensions of your scene, use the global mm_per_unit
  setting). The material's index of refraction also affects the appearance of
  the material, and is mandatory for SSLT materials.

  SSLT is now enabled only when a global_settings subsurface block is present;
  to enable SSLT but use the default settings, specify an empty block,
  i.e. "subsurface{}"

  Due to the experimental status of SSLT, there are currently some caveats:
  - Incorrect use may result in hard crashes instead of parse warnings.
  - Pigments having any zero color components currently don't play nice with
  SSLT; for example instead of "rgb 1" you should use something like
  "rgb <1,0.05,0.05>".
  - A Diffuse finish attribute of zero can cause the program to have an
  assertion failure.
  - changes to improve robustness regarding low translucency and/or high
  mm_per_unit settings for objects in general and blobs in particular
  added support for CSG (caveat: unions of overlapping components will cause
  unexpected results; use merge instead)

  Further Subsurface scattering improvements include:

  - added syntax to global subsurface block:

  global_settings { subsurface { radiosity BOOL } }

  specifies whether subsurface light transport effects should be applied to
  incoming radiosity-based diffuse illumination; if this setting is
  off (default), subsurface light transport effects will only be applied to
  direct illumination from classic light sources. Setting this to on will
  improve realism especially for materials with high translucency, but at a
  significant cost in rendering time.

  - added syntax to global radiosity block:

  global_settings {  radiosity { subsurface BOOL } }

  specifies whether radiosity sampling should honor subsurface light transport;
  if this setting is off (default), radiosity-based diffuse illumination is
  computed as if the surrounding objects had subsurface light transport turned
  off. Setting this to on may improve realism especially in the presence of
  materials with high translucency, but at some cost in rendering time.

  - Subsurface scattering is disabled in all quality levels except +Q9
    or higher.
  - More thorough fix to complement change #5425.
  - Minor changes to reduce intensity of patterned noise artifacts on
    subsurface textures.

Other Noteworthy
----------------

  - Added new "albedo" keyword, that can be used right after "diffuse",
    "phong" or "specular" to specify that the parameter is to be taken as the
    total diffuse/specular reflectance, rather than peak reflectance. E.g.:

    diffuse albedo 0.5 brilliance 2
    specular albedo 0.05 roughness 0.001
    phong albedo 0.02 phong_size 1000

    Note that for brilliance = 1, the "albedo" keyword has no effect on the
    diffuse parameter.

  - A major overhaul of iridescence feature, which used to be seriously flawed;
    syntax remains unchanged, except that both thickness and amount are now
    supposed to be specified in microns. The new irid_wavelength default value
    is now <0.70, 0.52, 0.48>, so iridescence effects will vary from previous
    versions.

  - Added support for tuning brightness of image-mapped sky spheres:
    Added "emission COLOUR" parameter to sky_sphere, defaulting to [rgb] 1.
    Higher values increase the sky sphere brightness accordingly, while lower
    values decrease it. While primarily intended for easy tuning of light probe
    skies, the parameter also works with procedural sky pigments.

  - Added three new "tiling" patterns:
    - pattern 25 type (N=6) produces a Penrose P1 tile
    - pattern 26 type (N=2) produces a Penrose P2 tile
    - pattern 27 type (N=2) produces a Penrose P3 tile

  - Added AMD optimizations for noise. Note that these are currently disabled.

Windows Source Build:
---------------------

  A subset of the Boost 1.45.0 and openEXR 1.6.1 libraries have been added to
  the windows source distribution so that users can easily build thier own
  statically linked binary from scratch. Added "Console" and "Console-SSE2"
  configurations to VS10 solution, but needs to be back-ported to VS8/9 as
  there is no debug configuration yet. Extensive testing still required ...
  expect shellout to be still dysfunctional.

Windows Crash Reports:
----------------------

  - The crash reporter tool has been reworked to always generate both full and
    mini dumps because often insufficient information was available to resolve
    the crash, consequently compression support was also added.
  - A windows editor fix for a problem that was reported in crashdump #111

Windows Installer:
------------------

  Introduced a new windows version NSIS based installer, further improvements
  pending. Currently there are a few caveats:

  - It won't ask you to uninstall the old beta (don't use MSI anymore)
  - It won't object if you try to re-install over the top of an existing install.
  - It also requires elevation on Vista and Windows 7 as it allows installation
  to the program files directory (the default now).

Fixed or mitigated the following reports:
-----------------------------------------

http://bugs.povray.org/task/9     FS#9     (sky_sphere brightness tuning)
http://bugs.povray.org/task/46    FS#46    (area_illumination enhancement)
http://bugs.povray.org/task/156   FS#156   (crash reading empty DF3 file)
http://bugs.povray.org/task/165   FS#165   (projected image_map is clipped)
http://bugs.povray.org/task/166   FS#166   (quick_color does not work)
http://bugs.povray.org/task/169   FS#169   (photon memory leak)
http://bugs.povray.org/task/185   FS#185   (wrong image resolution reported)
http://bugs.povray.org/task/190   FS#190   (photon message reporting)
http://bugs.povray.org/task/191   FS#191   (interpolated image_map artifacts)
http://bugs.povray.org/task/194   FS#194   (command line option change)
http://bugs.povray.org/task/196   FS#196   (subsurface seqmentation faults)
http://bugs.povray.org/task/197   FS#197   (-J option was a no-op)
http://bugs.povray.org/task/198   FS#198   (missing braces in funtion)
http://bugs.povray.org/task/199   FS#199   (scene file typos)
http://bugs.povray.org/task/200   FS#200   (Calibri TrueType font garbled)
http://bugs.povray.org/task/203   FS#203   (radiosity artifacts)
http://bugs.povray.org/task/204   FS#204   (--V is not Verbose=off on Unix)
http://bugs.povray.org/task/206   FS#206   (cannot open file error)
http://bugs.povray.org/task/208   FS#208   (use-after-free when returning)
http://bugs.povray.org/task/209   FS#209   (weighted texture of CSG)
http://bugs.povray.org/task/210   FS#210   (UV mapping broken for parametric)
http://bugs.povray.org/task/213   FS#213   (add check for ios failbit/badbit)
http://bugs.povray.org/task/214   FS#214   (failed to parse command-line)
http://bugs.povray.org/task/215   FS#215   (double error reporting)
http://bugs.povray.org/task/216   FS#216   (obsolete option in raddem.ini file)
http://bugs.povray.org/task/221   FS#221   (crash undefinded looks_like object)
http://bugs.povray.org/task/225   FS#225   (looks_like texture translate fix)
http://bugs.povray.org/task/235   FS#235   (unix segmentation fault)

Scene file updates and additions:
---------------------------------

Updated the tiling pattern scene file:
  ~scenes/textures/patterns/tiling.pov

Updated the SSLT scene file:
  ~scenes/subsurface/subsurface.pov

Added these mesh_camera scene files:
  ~scenes/camera/mesh_camea/ess/ess-ortho-camera.pov
  ~scenes/camera/mesh_camea/ess/ess-persp-camera.pov
  ~scenes/camera/mesh_camea/ess/ortho-camera.pov
  ~scenes/camera/mesh_camea/ess/persp-camera.pov

Added a missing scene file:
  ~scenes/bsp/Tango.pov

Added a new tiling pattern scene file:
  ~scenes/textures/patterns/tiling.pov

Fixed two macros in ~includes/shapes.inc:
  - HFCreate_ : output formatting
  - Bevelled_Text : suppress "bound_by" warnings

Removed an obsolete directive that aborted the render:
  ~scenes/animations/raddem/raddem.ini

Removed obsolete comments (Library_Path limitation) from povray.ini

-----------------------------------
Changes between 3.7.RC2 and 3.7.RC3
-----------------------------------

This release candidate is primarily to correct a bug in media that was causing
crashes. It also improves a performance issue related to output file caching.

Output File Caching
-------------------

The efficiency of the code for caching output files on disk has been improved.
In addition, the point at which an output file is cached has been changed from
a compiled-in number of pixels to a user-defined number of megabytes.

When rendering an image that has output to file turned on, POV-Ray will cache
the image in two places: firstly, a .pov-state file, which is always on disk.
This is not technically an image file but a record of the communication
between the internal frontend and backend, which also contains the image pixels.
This file is only ever needed if you wish to re-start a render using the +c
option. It is deleted upon successful completion of a render.

The second place an image is cached is in an image buffer, which contains only
the image pixels. This buffer is what is used to create the final output image
once a render completes. The buffer is stored in a neutral format (i.e. not in
any way related to the selected output file type), and may either be in RAM or
on disk.

Storing it on disk reduces performance slightly since POV-Ray has to perform
disk access to write it during render, then to read it when converting to the
final output format.

Storing it in memory removes the above performance penalty, but may add a worse
one if you are rendering at a very high resolution and the size of the resulting
memory buffer causes parts of the parsed POV-Ray scene to be swapped to a page
file by the operating system. This can slow down a render by several orders of
magnitude, depending on the circumstance.

The point at which POV-Ray will change from an in-memory buffer to a disk buffer
is controlled by the new Max_Image_Buffer_Memory INI parameter (+IM if specified
via the command-line). If not supplied, POV-Ray will default to 128mb. If supplied,
the number represents the approximate number of megabytes (1,048,576 bytes) that
POV-Ray will allow the internal image buffer to occupy. If an image exceeds this
size, the image buffer will be placed in a temporary file on disk instead. Note
that this decision is made upon the start of the render - the buffer does not grow
during render, but is pre-allocated to the size required to hold all the pixels.

As a guide, you can expect POV-Ray to use 20 bytes per pixel to store the image
during render. Thus, the default 128mb size allows an image of up to about 6.7
million pixels to be stored in RAM (approximately 2600 x 2600 pixels).

You should definitely consider reducing this default if your system is memory-
constrained or you are rendering a scene that generates a particularly large
dataset.

The value supplied to Max_Image_Buffer_Memory should be an integer greater than 0,
and represents megabytes (not bytes). If 0 is supplied, POV-Ray will never use
file-backing for the image buffer.

The windows version of POV-Ray has a small memory monitor in the statusbar. It
updates several times per second with an estimation of the amount of memory being
used by the application. You can use this as a guide to determine the amount of
RAM in use.

---------------------------------------
Changes between 3.7.beta.41 and 3.7.RC2
---------------------------------------

-----------------------------------------
Fixed or mitigated the following reports:
-----------------------------------------

  http://bugs.povray.org/task/185   FS#185   (wrong message about image resolution)
  http://bugs.povray.org/task/186   FS#186   (sub-polygon end points)
  http://bugs.povray.org/task/187   FS#187   (unix signal handling issue)
  http://bugs.povray.org/task/188   FS#188   (no_reflection broken)

  fixed crash found by crashdump #77 (platform base can be NULL before the image
  class gets destroyed in the case of unusual shutdown).

  fixed crash in editor where FormatMessage() fails (refer crashdump #76).

  using "color srgb" (or similar) before assumed_gamma was defined resulted in
  a hard crash; fixed by generating a proper parse error instead.

  fixed memory leak.

------------
Misc Changes
------------

  disable full memory allocation tracking on windows in favor of rougher
  estimate based on samples of peak memory usage from windows API.

  make windows status pane a bit wider and add process memory usage slot in
  status bar.

  go back to using the current version as the default language version and
  modify the warning messages associated with a missing or late #version.

  added updated windows help file.

  added very basic support for running shell-outs on unix.

  removed beta status, moving to RC. no more timeouts.

  benchmark results on windows are now copied to the clipboard.

  some photon fixes.

-----------
SDL Changes
-----------

  Gamma Handling:

    The assumed_gamma keyword is no longer deprecated; to the contrary, it is
    now considered mandatory if a #version 3.7 or higher is specified, and its
    absence will raise a "possible error" in this case, with a value of 1.0 being
    presumed. (Note that #version, too, is now mandatory, and its absence will
    raise a warning as well).

    The assumed_gamma value is now presumed to denote the "working color
    space", in which classic color literals are specified and color
    computations to be performed. Note however that this will give unrealistic
    results for any value other than 1.0.

    Colors specified using "srgb" & co. will be converted from sRGB to the
    working color space.

    image_map input files for which definitive implicit or explicit gamma
    information is available (either by file format specification like the HDRI
    formats, header information like PNG with sRGB or gAMA chunk, or a user
    override via the "gamma" keyword) will be converted to the working color
    space. If no definitive information is available, the respective files will
    be presumed to match assumed_gamma if #version is < 3.7 or unspecified, or
    any official recommendation if #version >= 3.7 is specified.

    height_field, bump_map and image_pattern input files will not be subject to
    gamma-adjustment, unless the user explicitly specifies an override via the
    "gamma" keyword; in that case, the file is presumed to match the gamma
    value specified, and converted to linear values, irrespective of
    assumed_gamma.

  Concerning anti-aliasing, for the decision whether to anti-alias the color
  values will be converted from the working color space to that specified by
  the Assumed_Gamma INI setting; the averaging of the samples however will be
  performed in the working color space.

    For render preview, the generated image will be converted from the working
    color space to that specified by the Display_Gamma setting. If
    Display_Gamma is not specified, a platform-specific default will be
    presumed.

    For file output, the generated image will be converted from the working
    color space to whatever the file format mandates (this applies to OpenEXR
    and Radiance HDR); if no such mandatory color space exists, the image will
    be converted into that specified by the File_Gamma setting. If File_Gamma
    is not specified either, the image will be converted into whatever is
    officially recommended for that file format, or the de-facto standard; if
    even that doesn't exist, no gamma adjustment is performed. In any case, if
    the file format provides a means to specify a gamma in the image header
    (this applies to PNG), the respective data is set according to whatever
    gamma the image is converted to, regardless of the working color space.

    If assumed_gamma is not specified, and #version is set to pre-3.7 or
    undefined, no gamma handling is performed at all.

    In terms of backward compatibility, this translates as follows:

    If assumed_gamma is not specified, and #version is set to pre-3.7 or
    undefined, full compatibility with 3.6 and earlier is maintaned.

    If assumed_gamma is specified and #version is set to pre-3.7 or undefined,
    compatibility with 3.6 is subject to the following restrictions: (a) full
    output file handling compatibility requires File_Gamma to be set to the
    same value as Display_Gamma (or left undefined if Display_Gamma is
    undefined), and (b) input file handling is not backward compatible in case
    of PNG files.

    If assumed_gamma is not specified and #version is set to 3.7 or higher,
    compatibility with 3.6 or earlier is not maintained.

--------------------------------------------
Changes between 3.7.beta.40 and 3.7.beta.41
--------------------------------------------

-----------------------------------------
Fixed or mitigated the following reports:
-----------------------------------------

  http://bugs.povray.org/task/179  FS#179  (unix version segfaults when $HOME not set)
  http://bugs.povray.org/task/182  FS#182  (multi-textured blobs in intersections / differences broken)

------------
Misc Changes
------------

  Raised max order of Poly object from 15 to 35.

  Deprecated histogram output options.

  Added new include file, "ior.inc", defining ior & dispersion constants for a
  lot of materials.

  Added new sample/test scene, "scenes/gamma/gamma_showcase.pov" (used in new
  gamma section in the docs)

  Several bug fixes for windows and generic core code.

-----------------
Dithering Support
-----------------

  Add support for output file dithering; dithering is controlled by the INI
  file settings "Dither=BOOL" and "Dither_Method=xx" as well as the command
  line option "+/-THxx", where xx is one of:

    "B2".."B4": Bayer pattern dithering using 2x2, 3x3 or 4x4 patterns, respectively
    "D1": simple 1-dimensional error diffusion dithering
    "D2": simple 2-dimensional error diffusion dithering (needs extra memory for 2 pixel rows)
    "FS": Floyd-Steinberg error diffusion dithering (needs extra memory for 2 pixel rows)

  The default is "-THfs", i.e. dithering is off, with Floyd-Steinberg being the
  default if only "+TH" is specified.

  Dithering works for all file formats except JPEG and OpenEXR (no intention to
  implement) as well as Radiance HDR (non-straightforward to implement); these
  file formats simply ignore the setting.

  Added dithering to reder preview, using 4x4 Bayer dithering.

  Display_Gamma now supports the "sRGB" option just as File_Gamma already did;
  besides "sRGB", "srgb" and "SRGB", any combination of upper-/lowercase
  letters is now recognized.

-----------
SDL Changes
-----------

  Added new way to describe a polynomial equation (the old way is still valid):

    polynomial { <order>, [xyz(<a>,<b>,<c>):<value>,]* [remaining as usual for poly]}

    Default value for all coefficient is 0.0;
    each xyz(): set the coefficient to <value> for x^a.y^b.z^c;
    (constant is xyz(0,0,0)). Ordering of xyz is irrelevant (but identical index keep only the last one)
    a sphere (radius 1...  x^2 + y^2 + z^2 -1 =0)
    polynomial{ 2, xyz(2,0,0):1, xyz(0,2,0):1, xyz(0,0,2):1, xyz(0,0,0):-1 }

  Updated colour syntax for gamma pre-corrected colours; dropped the "gamma" keyword
  there (it remains enabled for image input files) in favor of the following syntax:

        colour srgb <Rp,Gp,Bp>
        colour srgbt <Rp,Gp,Bp,T>
        colour srgbf <Rp,Gp,Bp,F>
        colour srgbft <Rp,Gp,Bp,F,T>

  where Rp,Gp,Bp are colour component values pre-corrected for a display
  conforming to the sRGB colour space, and F,T are linear colour component
  values.

  Implemented requirement for "#version 3.7" to be provided to obtain full v3.7
  functionality. Prior to a #version statement appearing, the version defaults
  to 3.62. Additionally, if the first #version appears after any other declaration,
  or #version does not appear at all, a post-parse warning is issued.

  Changed the mechanism to retrieve & format the current time from SDL; new
  syntax is as follows:

    - The keyword "now" evaluates to the time elapsed since 2000-01-01, 00:00:00
      GMT in days, with a precision of seconds or better.

    - The function "datetime(FLOAT [,STRING])" interprets the FLOAT as days
      since 2001-01-01, 00:00:00 GMT, and the STRING as a formatting string (same
      format and default as was previously taken by "now([STRING])").

  Consequently, "datetime(now)" does what previously "now()" did, and
  "datetime(now,STRING)" does what previously "now(STRING)" did.

  Disabled #default { image_map { gamma ... } } statement.

--------------------------------------------
Changes between 3.7.beta.39 and 3.7.beta.40
--------------------------------------------

-----------------------------------------
Fixed or mitigated the following reports:
-----------------------------------------

  http://bugs.povray.org/task/56   FS#56   (Crackle pattern memory allocation)
  http://bugs.povray.org/task/64   FS#64   (Add "POV-Ray" metatags to images)
  http://bugs.povray.org/task/80   FS#80   (Bad behavior for missing image file)
  http://bugs.povray.org/task/105  FS#105  (Output options not displayed)
  http://bugs.povray.org/task/134  FS#134  (INI option to add information to output images)
  http://bugs.povray.org/task/154  FS#154  (Installation on linux set wrong owner)
  http://bugs.povray.org/task/167  FS#167  (Core dump when rendering to huge dimensions)
  http://bugs.povray.org/task/168  FS#168  (noise_generator default broken)

------------
New Features
------------

  --------------------------
  Pavement & Tiling patterns
  --------------------------

  Tiling # (#: 1 to 24) provide 24 classical tiling pattern with 1 or more kind
  of tiles. The full map is used when rendering a tiling. All centers of tile
  is at i/num, border at (i+1)/num) (for i from 0 to num-1). The gradient on
  each tile is the same for every tiles on the same tiling. When more than one
  kind of tile is used (#), the border are at 1/#, 2/#, ... #-1/#

  Pavement: (using polymino paving the plane)

   * number_of_sides (3,4,6) : the basic tile is a triangle, a square or an
     hexagon

   * number_of_tiles (1 to 5 or 6): the number of basic tiles to combine together
     to make one real tile

   * pattern (depend on side & tile) (1 to ...): how the basic are combined
     together

     * exterior (1 to 3, irrelevant for hexagon)

   * interior (1 to 3)

   * form (1 to 3, or 1 to 4 for square)

  Variations on type of corner. 0 is plain, 1 is a straight cut, 2 is a curved cut.
    All complet sets are covered.

  ------------------------------
  Square and Triangular patterns
  ------------------------------

  Added square & triangular pattern (2D, in xz plane, 4 & 6 area in shape of
  squares and triangles)

  --------------
  Ovus Primitive
  --------------

  Added the ovus shape.

  It's like a torus, but in egg shape ...

    ovus { base_radius, top_radius }

  (top_radius < 2.0*base_radius or else it's just a sphere).

  ----------------------
  Fractal pattern update
  ----------------------

  Experimental, add exterior type 7 & 8 for fractal pattern, using the number
  of actual iteration to get out (=e) and the factor (=n). 7 gives back
  mod(e,n)/n (covering 0 to n-1/n), while 8 covers 0 to 1 with mod(e,n+1)/n.

  ----------------------------
  New windows priority setting
  ----------------------------

  Add new option to set render priority to background (only available on Vista
  or later).

  --------------------
  New animation option
  --------------------

  Added +STP / Frame_Step= animation option inspired from megapov with two
  restrictions: only positive step value are supported (forward, no backward
  rendering) and the value is not available in the SDL.

  -----------------------------------
  New render pattern and step options
  -----------------------------------

  Added new render_pattern (-RP<N>) option, where N may be:

    0: Left to right, top to bottom (default).

    1: Top to bottom, then left to right

    2: Closing from left & right to center, top & bottom alternatively
       to middle

    3: Starting at center-middle, going left & right, then to top & bottom.

    4: Closing top & bottom to middle, alternatively left & right to centre.

    5: Opposite of -4 (starting at middle-center).

  Added new render_block_step (-RS<N>), option.

    The block step is used to work out what block to render next, as an offset
    from the current block number (blocks are numbered from 0, which is the
    top-left of the image). The block size is determined by the existing
    render_block_size option, which defaults to 32x32 pixels. Blocks are
    allocated to render threads in the order specified by the combination
    of the render_pattern option and this option.

    With N > 0, it's about 1 square every N (N might get reduced to allow clock
    arithmetic to cover the whole picture). N must be pseudo-prime; at worst it
    is shrunk to 1).

  --------------
  Image Metadata
  --------------

  Most image formats now include metadata (BMP is a notable exception). This
  metadata contains the POV-Ray version, render date/time (GMT), platform
  (e.g. x86_64-pc-win), and compiler used to build the POV-Ray executable.

----------------
SDL Improvements
----------------

  Adding bitwise operation (bitwise_and(), bitwise_or(), bitwise_xor()),
  similar to max(). Not limited to 2 parameters.

  Add pre-declared variable "input_file_name", a token replaced by a string
  which is the name of the input file of the scene.

  Add new function now(), which can have a string parameter (but can also be
  used without; the parenthesis are mandatory in either case). When provided
  with a string, the value is used for formatting the time. Formatting
  documentation is the one of strftime() C function. Without a parameter, the
  format is "%Y-%m-%d %H:%M:%SZ". The time base is GMT.

-------------
Gamma Changes
-------------

  Removed file_gamma keyword. Input image file default can now be set via

        default { image_map { gamma FLOAT } }

    or

        default { image_map { gamma srgb } }

  For backward compatibility with legacy scenes, POV-Ray 3.7 will now mimick
  all the gamma handling of POV-Ray 3.6 if the scene has a #version statement
  specifying a version of 3.6x or earlier, and/or specifies an assumed_gamma,
  with the following exceptions:

    * If the scene overrides the default input file gamma, POV-Ray will fall
      back to the new gamma handling model.

    * If the scene is rendered using the File_Gamma INI file setting, or using
      an INI file setting or command-line option to specify a version of 3.7 or
      later, input file gamma handling will still mimick 3.6 behaviour, but
      output file gamma handling will use the new model.

    * PNG input file handling is not fully backward compatible.

  Due to architectural changes, bug fixes and improvements, backward
  compatibility for PNG input files is subject to the following exceptions:

    * For palette-based PNG files (an uncommon flavour of PNG), backward
      compatibility is provided only if assumed_gamma is not specified. (This is
      due to a POV-Ray 3.6 bug not mimicked by POV-Ray 3.7.)

    * For non-palette-based PNG files, backward compatibility is provided only
      if assumed_gamma is specified. (This is due to an architectural change that
      makes this overly difficult to mimick.)

    * For PNG files carrying both an sRGB chunk and a fitting gAMA chunk,
      results will slightly differ. (This is due to POV-Ray 3.7 recognizing sRGB
      chunks, which POV-Ray 3.6 did not do.)

    * For PNG files carrying an sRGB chunk but no gAMA chunk (or a wrong one),
      backward compatibility is not provided. (Again this is due to POV-Ray 3.7
      recognizing sRGB chunks.)

------------------
Misc Fixes/Changes
------------------

  Fixed divide-by-zero crash in editor support code (refer crash report #50).

  Expand uses of FixedSimpleVector<64> to 127 elements to alleviate issues
  with reports of 'out of memory' in some circumstances. This comes at the
  cost of using more memory per recursion level, though. Also updated the
  code to make sure hitting the internal limit of 127 elements is now clearly
  reported as an internal limit rather than a memory limit.

  Fixed bug causing interpolated image maps to be shifted by half a pixel, as
  described in http://news.povray.org/4bdad2a5@news.povray.org

  Improved alpha premultiplication handling for pattern images

  Updated support for file-backed RGBFT images to allow 64-bit seek offsets,
  and added code to automatically switch to using file-backed intermediate
  images when width >= 32 and pixel count >= 1024*1024. This will significantly
  reduce memory usage for large renders, at the cost of more I/O overhead.

  Fixed issue where a shutdown after a render that allocated a lot of memory
  blocks (or any other case where the shutdown takes more than five seconds)
  could throw an uncaught exception. This could then cause the 'terminated in
  an unusual way' windows error message.

  Revised Fractal fields in pattern structure to allow deeper iterations
  (past 32767, now upto 2^32-1) for fractal patterns.

--------------------------------------------
Changes between 3.7.beta.38 and 3.7.beta.39
--------------------------------------------

----------
Bugs fixed
----------

  http://bugs.povray.org/task/114  FS#114  (corrected 1 pixel error in mosaic preview)
  http://bugs.povray.org/task/155  FS#155  (changed Output_File_Type to type "n")
  http://bugs.povray.org/task/157  FS#157  (fix parse warnings)
  http://bugs.povray.org/task/158  FS#158  (wrong value to be reported for antialiasing gamma)
  http://bugs.povray.org/task/162  FS#162  (fix for Character 101 (0x65) not found)

  - Fixed some dormant photons code that, was broken with radiosity change #4761
  - Fixed a parser issue related to the obsolete "max_intersections" keyword.
  - A shellout fix.

------------
New Features
------------

  ---------------------------------------------------------------------------------
  Mesh Camera
  ---------------------------------------------------------------------------------

  Note: The mesh camera is an experimental feature introduced in version 3.7
  beta 39 and its syntax is likely to change. Additionally, many of the normal
  camera concepts presented in this section (such as location and direction)
  either do not work as they do for other cameras or do not work at all (for
  example, the concept of 'up' simply does not apply to a mesh camera). It should
  also be kept in mind that the camera has not yet been tested with many of
  POV-Ray's advanced features such as photons and radiosity, and more work in
  that area is likely to be needed.

  The mesh projection is a special camera type that allows complete control of
  the ray origin and direction for each pixel of the output image. The basic
  concept is to associate pixels with faces defined within a mesh or mesh2
  object. The mesh need not be instantiated in the scene, though it can be, and
  doing so can lead to some interesting uses, such as texture baking or
  illumination calculations.

  In its simplest form, each pixel of the output image is assigned to a face of
  the mesh according to (width * (int) y) + (int) x, however, more complex
  mapping is possible via multiple meshes and multiple rays per pixel. The type
  of mapping in use is determined by the distribution type parameter in the
  camera declaration. Except for mapping #3, the ray origin will be set to the
  centroid of the face, and the direction will be that of the face's normal. For
  mapping #3, barycentric co-ordinates are determined from the UV co-ordinates of
  the first face to match the X and Y position, and those are then converted to a
  position on the face which will serve as the ray origin. Support is provided to
  move the origin off the face along the normal, and to reverse the ray
  direction.

  For most of the distribution methods, any POV feature that causes sub-pixel
  positioning to be used for shooting rays (e.g. anti-aliasing or jitter) will
  not do anything useful, because X and Y are converted to integers for indexing
  purposes. At this time, no warning is issued if anti-aliasing or jitter is
  requested when rendering a non-applicable distribution; this may be added
  later.

  The syntax for the mesh camera is as follows:

  camera {
    mesh_camera {
      rays per pixel
      distribution type
      [max distance]
      mesh {
        MESH_OBJECT_IDENTIFIER
        [TRANSFORMATIONS]
      }
      [mesh ...]
    }
    [location]
    [direction]
    [smooth]
  }

  Rays Per Pixel
  --------------

  This float parameter controls the number of rays that will be shot for each
  pixel in the output image. Each distribution allows different values, but the
  minimum is always 1.

  Distribution Type
  -----------------

    This float parameter controls how pixels are assigned to faces as documented below:

    * distribution #0

      This method allows single or multiple rays per pixel, with the ray number
      for that pixel allocated to each mesh in turn. The index into the meshes is the
      ray number, where rays per pixel is greater than one, and the index into the
      selected mesh is the pixel number within the output image. If there is no face
      at that pixel position, the resulting output pixel is unaffected.

      You must supply at least as many meshes as rays per pixel. Each pixel is
      shot rays per pixel times, and the results averaged. Any ray that does not
      correspond with a face (i.e. the pixel number is greater than or equal to the
      face count) does not affect the resulting pixel color. Generally, it would be
      expected that the number of faces in each mesh is the same, but this is not a
      requirement. Keep in mind that a ray that is not associated with a face is not
      the same thing as a ray that is but that, when shot, hits nothing. The latter
      will return a pixel (even if it is transparent or the background color),
      whereas the former causes the ray to not be shot in the first place; hence, it
      is not included in the calculation of the average for the pixel.

      Using multiple rays per pixel is useful for generating anti-aliasing (since
      standard AA won't work) or for special effects such as focal blur, motion blur,
      and so forth, with each additional mesh specified in the camera representing a
      slightly different camera position.

      Note: It is legal to use transformations on meshes specified in the camera
      body, hence it's possible to obtain basic anti-aliasing by using a single mesh
      multiple times, with subsequent ones jittered slightly from the first combined
      with a suitable rays per pixel count.

    * distribution #1

      This method allows both multiple rays per pixel and summing of meshes, in other
      words the faces of all the supplied meshes are logically summed together as if
      they were one single mesh. In this mode, if you specify more than one ray per
      pixel, the second ray for a given pixel will go to the face at (width * height
      * ray_number) + pixel_number, where ray_number is the count of rays shot into a
      specific pixel. If the calculated face index exceeds the total number of faces
      for all the meshes, no ray is shot.

      The primary use for this summing method is convenience in generation of the
      meshes, as some modelers slow down to an irritating extent with very large
      meshes. Using distribution #1 allows these to be split up.

    * distribution #2

      Distribution method 2 is a horizontal array of sub-cameras, one per mesh (i.e.
      like method #0, it does not sum meshes). The image is divided horizontally into
      #num_meshes blocks, with the first mesh listed being the left-most camera, and
      the last being the right-most. The most obvious use of this would be with two
      meshes to generate a stereo camera arrangement.

      In this mode, you can (currently) only have a single ray per pixel.

    * distribution #3

      This method will reverse-map the face from the UV co-ordinates. Currently, only
      a single ray per pixel is supported, however, unlike the preceding methods,
      standard AA and jitter will work. This method is particularly useful for
      texture baking and resolution-independent mesh cameras, but requires that the
      mesh have a UV map supplied with it.

      You can use the smooth modifier to allow interpolation of the normals at the
      vertices. This allows for use of UV mapped meshes as cameras with the benefit
      of not being resolution dependent, unlike the other distributions. The
      interpolation is identical to that used for smooth_triangles.

      If used for texture baking, the generated image may have visible seams when
      applied back to the mesh, this can be mitigated. Also, depending on the way the
      original UV map was set up, using AA may produce incorrect pixels on the
      outside edge of the generated maps.

  Max Distance
  ------------

  This is an optional floating-point value which, if greater than EPSILON (a very
  small value used internally for comparisons with 0), will be used as the limit
  for the length of any rays cast. Objects at a distance greater than this from
  the ray origin will not be intersected by the ray.

  The primary use for this parameter is to allow a mesh camera to 'probe' a scene
  in order to determine whether or not a given location contains a visible
  object. Two examples would be a camera that divides the scene into slices for
  use in 3d printing or to generate an STL file, and a camera that divides the
  scene into cubes to generate voxel information. In both cases, some external
  means of processing the generated image into a useful form would be required.

  It should be kept in mind that this method of determining spatial information
  is not guaranteed to generate an accurate result, as it is entirely possible
  for a ray to miss an object that is within its section of the scene, should
  that object have features that are smaller than the resolution of the mesh
  being used. In other words, it is (literally) hit and miss. This issue is
  conceptually similar to aliasing in a normal render.

  It is left as an exercise for the reader to come up with means of generating
  pixel information that carries useful information, given the lack of light
  sources within the interior of an opaque object (hint: try ambient).

  Mesh Object
  -----------

  One or more mesh or mesh2 objects to be used for the camera. These will be
  treated differently depending on the distribution method, as explained above.
  Transformations on the meshes can be used here, and will reflect on the
  resulting image as it would be expected for a regular camera.

  Location
  --------

  With this special camera, location doesn't affect where the camera is placed
  per se (that information is on the mesh object itself), but is used to move the
  origin of the ray off the face, along the normal of that face. This would
  typically be done for texture baking or illumination calculation scenes where
  the camera mesh is also instantiated into the scene, usually only a tiny amount
  of displacement is needed. The X and Y for location is not currently used, and
  the Z always refers to the normal of the face, rather than the real Z direction
  in the scene.

  Direction
  ---------

  Like location, this doesn't correspond to the real direction vector of the
  camera. It serves only to reverse the normal of all the faces, if necessary. If
  the Z component is less than -EPSILON, then the rays will be shot in the
  opposite direction than they would otherwise have been. X and Y are not used.

  Smooth
  ------

  This optional parameter is only useful with distribution #3, and will cause the
  ray direction to be interpolated according to the same rules as are applied to
  smooth triangles. For this to work, the mesh must have provided a normal for
  each vertex.

  See the sample scene files located in ~scenes/camera/mesh_camera/ for additional
  usages and other samples of mesh cameras. There are also some useful macros to
  assist in generating and processing meshes for use as cameras.

  ---------------------------------------------------------------------------------

  Added support for focal blur with user-defined bokeh, using the following syntax:

    camera {
      // ... focal blur camera...
      bokeh {
        pigment { ... }
      }
    }

  If bokeh is specified, focal blur will use a custom sampling sequence based
  on the specified pigment's brightness in the range <0,0,0> to <1,1,0>, i.e.
  the unit square in the XY plane.

  ---------------------------------------------------------------------------------

  Introduced new framework for internal random number generators, intended for
  reducing the memory footprint (by sharing precomputed values among
  generators with identical parameters) as well as easier replacement of
  implementations.

  ---------------------------------------------------------------------------------

------------
Improvements
------------

  Radiosity improvements:

  - Removed the max 1600 count limit; if the count exceeds 1600, POV-Ray will
    now use a Halton sequence instead of the built-in sequence.

  - POV-Ray can now draw sample directions in a round-robin fashion from a
    larger pool, so that different samples can use different sets of sample
    directions, leveraging the benefit of the nearest_count mechanism.
    For this purpose, the count keyword syntax has been changed:

      count RAYS_PER_SAMPLE [, DIRECTION_POOL_SIZE ]

  - Added importance sampling to radiosity; full ray computations are
    performed only for a certain portion of sample rays, depending on the
    importance of the first object each ray encounters. Importance can be
    assigned on a per-object basis using the followng syntax (using a sphere
    as an example):

      sphere { ... radiosity { importance IMPORTANCE } }

    where IMPORTANCE is a value in the range from >0.0 to <=1.0 specifying the
    percentage of rays to actually compute on average. A particular ray will
    only be fully computed if it is within the first COUNT*IMPORTANCE rays of
    the sampling sequence; due to the low-discrepancy sub-random nature of the
    sequence, this is mostly equivalent to a per-ray weighted random choice,
    while maintaining a low-discrepancy uniform distribution on a per-object
    basis. Rays actually computed are weighted to compensate for those
    not computed.

    Objects derived from previously defined objects will default to the
    "inherited" importance. CSG components without an explicit importance will
    default to their parent object's importance. Other objects normally
    default to an importance of 1.0, but this can be changed in a
    default {} block:

      default { radiosity { importance DEFAULT_IMPORTANCE } }

    NOTE: The "radiosity on|off" feature for objects (specifying whether an
    object shall receive radiosity illumination) is currently NOT available.
    Depending on user feedback, it will be substituted with some keyword
    within the object-specific radiosity{} block, or dropped completely.

  - Some more minor modifications.

  ---------------------------------------------------------------------------------

  Improved focal blur:

  - Modified code to generate extra samples in a circular rather than square
    pattern when blur_samples is not 4, 7, 19 or 37, leading to a circular
    rather than square bokeh.

  - Modified the code that re-placed an extra sample if it would be close to
    another one, in order to get rid of the lower-right bias the old
    code produced.

  - Extra samples are now generated from a halton sequence rather than a
    random stream.

  - Modified blur_samples syntax to optionally specify a minimum number of
    samples to be taken before testing against confidence/variance settings
    (default is 4 if blur_samples maximum is <7, otherwise 7), to provide a
    means to get rid of stray non-blurred pixels. The new syntax is:

      blur_samples [ MIN_SAMPLES, ] MAX_SAMPLES

  - Eliminated the VEC2 type in favor of Vector2d.

  - Simplified a few statements and did a bit of cleanup.

  ---------------------------------------------------------------------------------

  SSLT improvements:

  - Fixed a bug in SSLT code that caused the single-scattering
    term to be ignored.

  - Using halton sequence instead of random generator for picking sampling
    directions, to reduce visible patterns in noise.

  ---------------------------------------------------------------------------------

------------
Misc Changes
------------

  - Changed radiosity defaults to "always_sample off" and "recursion_limit 2"
  - Changed Output_File_Type to type "n" in ~scenes/advanced/benchmark.ini
  - Updates in preparation for provision of crash upload utility.
  - Installer changes see article <web.4c558a54f4269f7c380f8080@news.povray.org>

--------------------------------------------
Changes between 3.7.beta.37 and 3.7.beta.38
--------------------------------------------

----------
Bugs fixed
----------

  http://bugs.povray.org/task/103  FS#103  (JPEG output does not conform to baseline JFIF standard)
  http://bugs.povray.org/task/104  FS#104  (Output file gamma broken for File_Gamma=1.0)
  http://bugs.povray.org/task/107  FS#107  (Failed to parse INI file, over network)
  http://bugs.povray.org/task/111  FS#111  (Remove_Bounds=off / -UR does not work properly)
  http://bugs.povray.org/task/112  FS#112  (OpenEXR alpha is only written when it shouldn't be)
  http://bugs.povray.org/task/113  FS#113  (Multi-layered reflections broken)
  http://bugs.povray.org/task/114  FS#114  (Mosaic Preview not displaying properly" for unix systems)
  http://bugs.povray.org/task/116  FS#116  (Assertion fails when using 'filter all' with small-palette images)

  Fixed an issue with SSLT that could cause rendering threads to hang
  Fix crash reported in http://news.povray.org/4bd949b3@news.povray.org
  Fixed error in windows version expiry test causing timeout message from 1 July.
  Fixed UV mapping for bezier spline lathe.

--------------------------
Changes to Windows version
--------------------------

  Expanded number of available insert menu ID's to about 9000.
  Added support for loading of JPG and PNG files as insert menu hints. The
  search order is PNG, then JPG and if they don't exist then BMP.

  Windows editor tab/indent settings are no longer per-file+global default;
  changing one affects all files.

  Added display of filename when hovering over an editor tab.

  Added right-click menu to editor tabs allowing opening of folder in explorer
  and copy of filename to clipboard.

  Default output file type is now PNG (SYS format is still mapped to BMP though).

----------------------------------------
Gamma and color-handling related changes
----------------------------------------

  Changed effect of filter in a layered-pigment sky_sphere to match the
  behavior of a corresponding layered-texture large regular sphere. (The old
  behavior, though probably having been unintentional, is automatically
  re-activated for backward compatibility when #version < 3.7 is specified.)

  Partial fix for broken alpha channel output; v3.6 behavior is now reproduced
  exactly (including bugs), regardless of version. Further changes will address
  the premultiplied-alpha issue (which was already handled wrong in 3.6) and
  possibly add options for use cases where v3.6 behavior might be undesired.

                                     -----

  Changes to input image transparency handling:

    For material_map, /no/ alpha premultiplication handling is done whatsoever;
    instead, the data as stored in the file is used.

    For bump_map and image_pattern, images with alpha channel are treated as if
    they had a black background (unless the alpha channel itself is used).

                                     -----

  Changed alpha handling for image file input and output:

    Previous versions of POV-Ray always expected straight (non-premultiplied)
    alpha for file input, while always writing associated (premultiplied) alpha
    for output; this has been changed on a per-file-format basis to use the same
    alpha handling mode for in- and output alike:

    - PNG will use straight alpha as per specification;

    - OpenEXR and TIFF will use associated alpha as per specifications;

    - TGA and BMP 32-bit RGBA (an inofficial extension to BMP) will use
      straight alpha, retaining file input compatibility for now, until a final
      decision has been made on these formats.

    When generating non-premultiplied alpha output to a classic
    low-dynamic-range file format (e.g. PNG), transparency of particularly bright
    areas will now be reduced, in order to better preserve highlights on
    transparent objects. (Note that this mechanism has some limitations with
    colored highlights.)

    When used with file formats for which alpha output is currently not
    supported by POV-Ray (or only via an inofficial extension, as with BMP),
    turning on alpha output via Output_Alpha=on or +UA will now generate a
    warning.

                                     -----

  Changed antialiasing to compare gamma-adjusted colours instead of linear
  colours, to improve antialiasing of darker regions.

  Note that this gamma-adjustment is only applied to copies of the sample
  values, and does not affect averaging of the sample values, which is still
  performed on the original linear data. It is also independent of both preview
  display and output file gamma.

  The antialiasing gamma-adjustment is controlled by the new ini-file /
  command-line options "Antialias_Gamma=x" and "+AGx" respectively, defaulting
  to 2.5. Note that this differs from Display_Gamma and File_Gamma defaults, as
  it is intended to fit human vision rather than typical CRT characteristics.
  Nevertheless, the value specified is once again the inverse of the gamma
  actually applied, in order to use the more familiar value range.

                                     -----

  Changed input file gamma syntax for individual files; as an alternative to
  the "file_gamma" keyword, the parser will now also accept the "gamma" keyword
  originally introduced for specifying gamma in color values. (To specify the
  default input file gamma in the global_settings section, "file_gamma" is
  still mandatory though, as "gamma" would be ambiguous and misleading.)

                                     -----

  Added "gamma" keyword to specify gamma pre-corrected colours. The colour
  syntax is extended as follows:

      COLOR_BODY:
        COLOR_VECTOR [GAMMA] |
        COLOR_KEYWORD_GROUP |
        COLOR_IDENTIFIER [GAMMA]
      ...
      COLOR_KEYWORD_ITEM:
        COLOR_IDENTIFIER       |
        red Red_Amount         |
        blue Blue_Amount       |
        green Green_Amount     |
        filter Filter_Amount   |
        transmit Transmit_Amount |
        GAMMA
      GAMMA:
        gamma Gamma_Value |
        gamma srgb

    Specifying "gamma Gamma_Value" indicates that the colour components are
    gamma-precorrected for a display gamma of Gamma_Value, instructing POV-Ray to
    automatically convert the colour components to linear values using the
    following formula:

      Effective_Red_Amount      = pow ( Red_Amount,   Gamma_Value )
      Effective_Green_Amount    = pow ( Green_Amount, Gamma_Value )
      Effective_Blue_Amount     = pow ( Blue_Amount,  Gamma_Value )
      Effective_Filter_Amount   = Filter_Amount
      Effective_Transmit_Amount = Transmit_Amount

    Likewise, specifying "gamma srgb" indicates that the colour components are
    gamma-precorrected using the sRGB transfer function (being roughly, but not
    quite, equivalent to a Gamma_Value of 2.2).

    Note that gamma is NOT an additional component, but rather modifies the
    interpretation of the other colour keywords. For instance, the following
    statements are all fully equivalent:

      #declare Foo = colour rgbt <0.2, 0.3, 0.4, 0.5> gamma 2;
      #declare Foo = colour rgbt <0.04,0.09,0.16,0.50>;
      #local Fnord = colour rgbt <0.2, 0.3, 0.4, 0.5>; #declare Foo = colour Fnord gamma 2;

    Also note that specifying gamma does not affect the filter or transmit components.

                                     -----

  Added "premultiplied BOOL" parameter to input image file syntax.

    Like the gamma/file_gamma parameter, it must immediately follow the filename
    (though the order of gamma/file_gamma and premultiplied does not matter).

    The boolean parameter specifies whether the file is stored in premultiplied
    ("associated") or non-premultiplied ("straight") alpha format, overriding the
    file format specific default. (This keyword has no effect on files without an
    alpha channel.)

                                     -----

  Added support for using the sRGB transfer function for output file gamma;
  syntax is "File_Gamma=sRGB". ("SRGB" and "srgb" are supported as well.)

    Note: When "File_Gamma=sRGB" is used with PNG output file format, POV-Ray
    writes an sRGB chunk, thereby claiming that the output conforms to the sRGB
    color space; however, this claim is not necessarily true, as POV-Ray is
    currently not color space aware; it depends on whether your scene input data
    conforms to the sRGB color space.

    NB: The other gamma INI file parameters (Antialias_Gamma and DisplayGamma)
    do NOT support the "sRGB" value at present.

------------
Misc Changes
------------

  Added "#declare atand = function (x) {degrees(atan(x))} " to "math.inc".

  Add special handling for INI lines that are shell-out commands and re-implement
  support for shellouts.

  Implemented bicubic image interpolation as interpolation type 3.

  Changes to sky_sphere handling:

    Using filter in a sky_sphere with layered pigments now has the same effect
    as in a large sphere with a multi-layered texture. (For compatibility with
    legacy scenes, specifying a #version < 3.70 will revert to the old, poorly
    specified behavior.)

    Using Output_Alpha=on with legacy scenes (#version < 3.70) will now
    suppress sky spheres and background except in reflections, for backward
    compatibility with v3.6.

  Various output file type-related changes:

    When specifying an input image in SDL without a file type (neither via type
    keyword nor via extension), parser would not fall back to system default
    (broken since change #4932); fixed.

    When specifying an IFF input image in SDL, POV-Ray would instead attempt to
    read it as a TIFF file; should be fixed (not that anybody would probably care
    these days...).

    Some code pertaining to histogram output was not updated with change #4932;
    fixed. (no symptoms there, as histogram output is presently out of order
    anyway)

    Validity check for Grayscale_Output setting was broken with change #4932; fixed.

    Disabled chroma sub-sampling in JPEG output; reduced default quality setting
    from 95% to 85% to retain same overall quality & file size.

-----------------
Radiosity Changes
-----------------

  Modified radiosity pretrace mechanism:

    POV-Ray will now create only one set of threads for the whole pretrace,
    instead of one set for each pretrace step; likewise, progress report will
    pertain to the whole pretrace rather than each step; POV-Ray will no longer
    wait for a pretrace step to be fully completed, and instead assign threads to
    the next step as soon as all blocks of the previous step are either finished
    or already assigned.

    Implemented adaptive pretrace. When a second parameter is specified after
    the "nearest_count" keyword, pretrace will stop re-iterating over areas
    where, on average, that many (average-quality) samples are already present
    per ray.

                                     -----

  Parser now checks for plausible relation between radiosity minimum_reuse and maximum_reuse:

    If ony one value is specified, parser will warn if minimum_reuse > maximum_reuse/2,
    and adjust the unspecified value accordingly.

    If both values are specified, parser will warn if minimum_reuse > maximum_reuse/2,
    but not modify any of the values; if minimum_reuse >= maximum_reuse; the parser will
    raise an error.

------------------------------
Other SDL Changes/Enhancements
------------------------------

  Added #elseif statement; the #if, #ifdef and #ifndef directives syntax is
  changed as follows:

    IF_DIRECTIVE:
      #if ( Cond ) TOKENS... [ELSE_DIRECTIVE] #end
    IFDEF_DIRECTIVE:
      #ifdef ( IDENTIFIER ) TOKENS... [ELSE_DIRECTIVE] #end
    IFNDEF_DIRECTIVE:
      #ifndef ( IDENTIFIER ) TOKENS... [ELSE_DIRECTIVE] #end

    ELSE_DIRECTIVE:
      #else TOKENS... |
      #elseif ( Cond ) TOKENS... [ELSE_DIRECTIVE]

  Example:

    #if (Foo)
      #debug "Foo is true\n"
    #elseif (Bar)
      #debug "Foo is false, but Bar is true\n"
    #else
      #debug "Foo and Bar are both false\n"
    #end

                                     -----

  Added "emission" parameter to the finish block; syntax and effect are
  virtually identicall to "ambient", except that "emission" is unaffected by
  the global "ambient_light" parameter, which will now effectively be set to 0
  if radiosity is active (except in legacy scenes having #version set to < 3.70).

  The intention is to simplify the use of materials designed for non-radiosity
  scenes in scenes with radiosity, or the design of scenes that can be rendered
  with or without radiosity.

--------------------------------------------
Changes between 3.7.beta.35 and 3.7.beta.37
--------------------------------------------

  Partially fixed the following bugs:

    http://bugs.povray.org/task/81   FS#81  (sphere_sweep generating artifacts)
    http://bugs.povray.org/task/93   FS#93  (Photons are unnaturally amplified by pass_through objects)
    http://bugs.povray.org/task/102  FS#102 (#switch directive parsing problem)

  Fixed the following bugs:

    http://bugs.povray.org/task/67   FS#67  (Alpha channel in image map is ignored for shadows)
    http://bugs.povray.org/task/78   FS#78  (Wrong rendering of BeamTest-Scene in 3.7.beta.35a)
    http://bugs.povray.org/task/83   FS#83  (Redundant code in pvengine.cpp) (removed apparently duplicate
    http://bugs.povray.org/task/88   FS#88  (File output code does not properly handle negative color values)
    http://bugs.povray.org/task/89   FS#89  (PPM output garbled for bit depths other than 8 bits)
    http://bugs.povray.org/task/90   FS#90  (POV-Ray accepts additional patterns after (slope))
    http://bugs.povray.org/task/92   FS#92  (Sphere_Sweep Bug)
    http://bugs.povray.org/task/94   FS#94  (Unexpected refraction angle in interfaces with changing IOR <> 1.0)
    http://bugs.povray.org/task/95   FS#95  (Photons are over-attenuated by semi-transparent surfaces)
    http://bugs.povray.org/task/97   FS#97  (Forward-slash pathnames not fully supported in Windows version)
    http://bugs.povray.org/task/100  FS#100 (cutaway_textures)

  Implemented the following enhancement requests:

    http://bugs.povray.org/task/84    FS#84  (A for-loop construct)

  Photon changes
  --------------

    Refer FS#93 (Photons are unnaturally amplified by pass_through objects)

    As the error is also present in POV-Ray 3.6, behavior has necessarily
    changed with this fix; pass_through objects will now affect the color of
    photons on their way to their target, according to pigment filter/transmit,
    interior fade, and media (which implies that opaque objects will block
    photons even when declared pass_through); it needs to be seen whether this
    new behavior will be accepted by the users, or whether some additional
    mechanism will have to be implemented to choose between old and new
    behavior for compatibility with legacy scenes. At present, behavior can
    only be changed at compile time with the preprocessor defines PT_FILTER_BEFORE_TARGET
    and PT_AMPLIFY_BUG in photons.cpp.

  Radiosity changes
  -----------------

    When a new sample has been gathered after sample lookup returned insufficient
    samples, sample lookup is no longer run again; instead, the new sample is
    interpolated with the results of the earlier lookup.

    The actual number of samples required to satisfy the reuse_count setting is
    now influenced by sample quality, with high-quality samples reducing the
    effective number of samples required (down to 1/4 of the parameter value in
    extreme cases) and low-quality samples increasing the number. Note that this
    may change the balance between speed and quality for some scenes.

    The maximum_reuse parameter now governs the maximum effective radius of a
    sample more directly.

    Trimmed down radiosity sample memory footprint a bit.

    Improved pretrace "pixel" coordinates computation

  New features
  ------------

    AOI Pattern:

      Implemented AOI pattern (thanks to Grimbert Jerome for most of the code);
      the syntax is as follows:

        pigment { aoi pigment_map { ... } }
        normal { aoi normal_map { ... } }
        texture { aoi texture_map { ... } }

      The pattern gives a value proportional to the angle between the ray and the
      surface; for consistency with the slope pattern, values range from 0.5 where
      ray is tangent to the suftace, to 1.0 where perpendicular; in practice,
      values below 0.5 may occur in conjunction with smooth triangles or meshes.

      (Note that this differs from the current MegaPOV implementation, where the values
      range from 0.5 down to 0.0 instead.)

    Slope Pattern extension:

      Extended slope pattern to specify a reference point instead of a direction;
      the new syntax is as follows:

        slope { point_at <ReferencePoint> [, Lo_Slope, Hi_Slope] }

      (Note that this variant currently does *not* allow for the "altitude" keyword to be used.)

      The functionality is similar to MegaPOV's "aoi <ReferencePoint>" pattern,
      except that the values are reversed, i.e. range from 0.0 for surfaces
      facing away from the point in question, to 1.0 for surfaces facing towards
      that point; thus, "slope { <Vector> }" and "slope { point_at
      <Vector>*VeryLargeNumber }" have virtually the same effect.

  Other SDL changes
  -----------------

    Modified #break semantics; the #break directive can now be used:

        - anywhere within a #case or #range block, to skip to the end of the
          #switch directive (previously, #break was only useful right before the next
          #case, #range or #else directive, to indicate that a slip-through was not
          desired);

        - anywhere within a loop block (both #while and #for), to preliminarily
          terminate the loop; and

        - anywhere within a #macro block, to preliminarily terminate the macro.

      Example for the use in a loop:

        #local R = seed(4711);
        #for (I, 1, 100)
          #if (rand(R) < I/1000)
            #break // terminate loop early
          #end
          #debug concat(str(I,0,0), " iterations and counting\n")
        #end

      Where multiple #switch, loop and/or #macro blocks are nested, #break will
      leave only the innermost of these.

    Implemented a #for loop construct (see FS#84); the following syntax -

        #for (Identifier, Start, End [, Step])
          //...
        #end

      is now available for simple loops incrementing Identifier from Start to End
      (inclusive) with the given Step size (default: +1.0). Basically, it works the
      same as the classic #while pattern:

        #local Identifier = Start;
        #while (Identifier <= End)
          //...
          #local Identifier = Identifier + Step;
        #end

      Some additional notes:

        - If Step is negative, comparison will be automatically adjusted to match a
          "countdown" pattern.

        - Start, End and Step are evaluated only *once*.

        - The loop counter is a full-fledged local variable. Any local variable of
          the same name already defined before the loop *will* be overwritten without
          warning (note that in the main scene file, all local variables outside of
          macros are effectively global); inside the loop, any tampering with the
          variable is possible for effect, as long as it is defined as a local numeric
          variable at the end of each iteration.

        - After the loop has terminated, the variable will remain defined, typically
          holding the value End+Step.

        - The loop counter must *not* be an array element.

  Image output changes
  --------------------

    Image file output now uses the GammaCurve mechanism already in use for
    image file input, to allow for arbitrary transfer functions (e.g. as used by
    sRGB) in the future.

    Output/histogram file type is now identified by the command line / INI
    options parser, removing some uglies from the code and allowing for easier
    maintenance of file type letters.

    Radiance HDR image output no longer writes the proprietary GAMMA header field.

    PPM image output now supports 16-bit greyscale output (effectively writing a
    PGM file instead), to be activated via the "Greyscale_Output=on" option or
    the "+FPg" file type switch.

--------------------------------------------
Changes between 3.7.beta.35 and 3.7.beta.35a
--------------------------------------------

Fixed an axis problem with cones.
Fixed a crash observed in fish13.pov (but which could happen in many scenes).

-------------------------------------------
Changes between 3.7.beta.34 and 3.7.beta.35
-------------------------------------------

  Fixed the following bugs:
    http://bugs.povray.org/task/10
    http://bugs.povray.org/task/32
    http://bugs.povray.org/task/48
    http://bugs.povray.org/task/49
    http://bugs.povray.org/task/51
    http://bugs.povray.org/task/52
    http://bugs.povray.org/task/53
    http://bugs.povray.org/task/55
    http://bugs.povray.org/task/57
    http://bugs.povray.org/task/59
    http://bugs.povray.org/task/61
    http://bugs.povray.org/task/73

  Implemented some media improvements that may significantly speed up scenes
  using both "heavyweight" averaged or pattern-mapped textures (e.g.
  micronormals) and interior media.

  Subsurface light transport code should now properly handle light attenuation
  due to distance, spotlight falloff or intervening non-opaque objects
  (including media and projected_through objects). Diffuse ambient illumination
  is also supported to some extent (multiple-scattering term only) when
  radiosity is turned on (however, it does not actually call radiosity code at
  present).

  Various bug fixes and minor improvements in input file reading code.
  Added "out-of-the-box" transparency support for GIF files.
  Added support for PNG sRGB chunks.

  NOTE: Non-legacy scene default gamma handling for image input files has
  changed significantly from previous betas, affecting all file formats except
  OpenEXR, Radiance HDR and (with minor differences) most flavors of PNG; there
  will be NO corresponding warnings. See below for more detail.

  ---------------------------------------------------
  Changes to improve input image file gamma handling.
  ---------------------------------------------------

  Input image files not carrying unambiguous gamma information will now be
  assumed to match a common gamma setting, and gamma-adjusted accordingly; this
  common input file gamma setting can be specified in the scene file using the
  following syntax:

    global_settings {
        file_gamma GAMMA
    }

  where GAMMA is either a numeric expression specifying the approximate display
  gamma for which input files are assumed to be gamma pre-corrected, or the
  keyword 'srgb' indicating that input files are assumed to match the sRGB
  standard. (In the latter case, gamma adjustment is applied according to the
  sRGB standard, instead of approximating with a gamma 2.2 power-law function.)
  The default setting is sRGB.

  Regardless of this global setting, gamma correction is not applied if the
  image input file is obviously used as a mere data container, such as when
  immediately used in a height field.

  Default gamma handling rules for any image input file can be overridden by
  specifying 'file_gamma GAMMA" immediately after the file name, e.g.:

    image_map {
        jpeg "foobar.jpg" file_gamma 1.8
        interpolate 2
    }

  This also applies to contexts where gamma adjustment is not normally applied,
  e.g. file formats that are defined to be encoded linearly, or files used in
  height fields, to simplify handling of files not conforming to standards.

  NOTE: Gamma handling for PNG input files has changed as follows in legacy
  ('#version 3.6') scenes:

  - In the absence of an 'assumed_gamma' statement, non-indexed PNG files with
    a gAMA chunk (i.e. virtually all PNG files) will appear far brighter than
    with POV-Ray 3.6.

  - In the presence of an 'assumed_gamma 1.0' statement, indexed PNG files
    (uncommon) will appear darker than with POV-Ray 3.6.

  - In the presence of an 'assumed_gamma 2.2' statement, PNG files with a gAMA
    lower than 2.2 (uncommon) will appear darker than with POV-Ray 3.6.

  - PNG files with an sRGB chunk but no gAMA chunk may appear significantly
    different than with POV-Ray 3.6.

  - PNG files may generally appear slightly different than with POV-Ray 3.6.

  A warning will be printed in these cases, except for the latter.

-------------------------------------------
Changes between 3.7.beta.33 and 3.7.beta.34
-------------------------------------------

  Fixed following bugs:
    http://bugs.povray.org/task/39
    http://bugs.povray.org/task/40

  Added support for diffuse backside illumination:

    To model thin, diffusely-translucent objects (e.g. paper, curtains, leaves
    etc.), an optional 2nd float parameter has been added to the "diffuse"
    finish statement to control the effect of illumination from the back of the
    surface. The default value is 0.0, i.e. no diffuse backside illumination.
    For realistic results, the sum of both parameters should be between 0.0 and
    1.0, and the 2nd parameter should be the smaller of the two.

    Note: This feature is currently experimental and may be subject to change.
    In particular, the syntax as well as interoperation with double_illuminate,
    multi-layered textures or conserve_energy are still under investigation.

    A new sample scene, "advanced/diffuse_back.pov", has been provided to
    illustrate this new feature.

    New option added speed up radiosity pretrace:

      As some computations don't contribute to the generation of radiosity
      samples, they can safely be skipped during radiosity pretrace to gain
      some speed if the pretrace's other role as a coarse preview is not
      required.

      The following .ini file / command line options control whether pretrace
      performs all computations so it can double-feature as a coarse preview
      ("vain pretrace"):

        Radiosity_Vain_Pretrace=bool   turns vain pretrace on/off
        +RVP                           turns vain pretrace on (default)
        -RVP                           turns vain pretrace off

    Note that with vain pretrace off, preview will look remarkably odd during
    the radiosity pretrace phase; this is normal, and no reason to be alarmed.

    At the moment, turning vain pretrace off will affect only classic lighting
    computations (diffuse lighting, higlights and iridescence); other features
    expendable during pretrace may follow in future versions.

  Windows console version now sends stream output to stderr by default.

-------------------------------------------
Changes between 3.7.beta.32 and 3.7.beta.33
-------------------------------------------

  Fixed following bugs:
    http://bugs.povray.org/task/13 (4k files crash in Windows 64-bit editor)
    http://bugs.povray.org/task/14 (coincident transparency issue)
    http://bugs.povray.org/task/15 (julia fractal, trace and inside cause crash)
    http://bugs.povray.org/task/16 (reflective texture map crash)
    http://bugs.povray.org/task/17 (square blotches in transparency)
    http://bugs.povray.org/task/21 (unix scripts have wrong version set)
    http://bugs.povray.org/task/24 (isosurface, bounding box & threads)
    http://bugs.povray.org/task/31 (function pattern in image map)
    http://bugs.povray.org/task/32 (tiff file extension error)
    http://bugs.povray.org/task/33 (parse accepting invalid vector float components)
    http://bugs.povray.org/task/34 (could not link against boost_thread-boost_thread)

  Improved support for image output to stdout/stderr for supported file types.
  This does not implement progressive output - the image is only written after the
  render completes. Progressive output will be added in a later beta. Also, don't
  fclose stream if it's stdout, stderr or stdin, which fixes some issues with using
  stdout for animations. Also adds support for image output to stderr.

  Optimized the way imageProcessing handles creating new images; this should reduce
  the chance of an out-of-memory error when rendering with image output enabled.

  Added support for file-backed RGBFT image container; this is used for intermediate
  image storage if allocating a memory-backed one fails. This ought to significantly
  reduce "out of memory"-type errors, particularly "cannot allocate intermediate image
  storage". This implementation is basic in that it doesn't support large files (anything
  more than what fseek/fwrite etc can handle) and only buffers a single line. A better
  solution to the intermediate image storage issue is to go away from using an image
  container and cache the render blocks on disk instead, using a class that can stream
  fully-completed rows to the image output code (required for writing to stdout to work
  properly again).

  Added some more radiosity stats for performance tweaking

  On unix, drop support for --with-boost-src configure option.
  Note: with this change, the libraries/ folder is no longer distributed.
  Also get rid of --disable-vsnprintf-check and unimplemented SVGA support
  (--with-svga).

  Fixed ARRAYS_WriteDF3 macro (16-bit depth output and parse warning).

  Added no_radiosity keyword, as known from MegaPOV:
    Specifying "no_radiosity" in an object block makes that object invisible to radiosity
    rays, in the same way as "no_image", "no_reflection" and "no_shadow" make an object
    invisible to primary, reflected and shadow test rays, respectively.

  Revival of Radiosity Load/Save + various other radiosity code changes:

    The following .ini / command line parameters are recognized:

      Radiosity_File_Name=<name>" or "+RF<name>" to set the cache file name;
      Radiosity_From_File=<on/off>" or "+RFI" to enable reading the radiosity file at startup
      Radiosity_To_File=<on/off>" or "+RFO" to enable writing new samples to the radiosity file

    NOTE: The parameter names are preliminary, and may still be subject to change; there is
    a potential conflict between the shorthand forms)

    If both +RFI and +RFO are specified, new samples gathered are appended; otherwise, +RFO
    causes the file to be overwritten if it exists.

    New samples gathered are written whenever an SMP block is completed. Tests indicate
    that this is almost neutral regarding performance, compared to operation with radiosity
    file output disabled.

  New radiosity "high reproducibility" mode: when specifying "High_Reproducibility" or "+HR"
  on the command line, POV-Ray will spend extra effort to make sure renders are deterministic
  despite SMP (currently, radiosity is the only code to use this flag; in HR mode, radiosity
  pretrace starts out with fewer threads, and some extra rules are imposed on sample re-use
  that may cause surplus samples to be gathered).

-------------------------------------------
Changes between 3.7.beta.31 and 3.7.beta.32
-------------------------------------------

Added ARRAYS_WriteDF3 macro to arrays.inc for writing an array to a df3 file.

Fixed bug creating artifacts in output file when mosaic preview is used with +EP2 and -A.

Several Unix build fixes.

Added radiosity octree performance stats and fixed stats for max trace level & parse time.

Made some improvements to performance in crackle cache, and optimised the management of the
  crackle cache size by setting limits in megabytes (currently per-thread and not user-
  settable: this will change).

-------------
Binary #write
-------------

It is now possible to write 8, 16 and 32-bit words to an external file. These
words may be arranged in either little or big-endian fashion.

Placing one of the following keywords in the argument list of a #write
statement causes the values up to the next comma to be written in binary
format, using 2's complement integer representation, rounded to the nearest
integer in the representable range:

  uint8              - unsigned byte (0..255)
  sint8              - signed byte (-128..127)
  uint16be, uint16le - unsigned 16-bit word (0..65535)
  sint16be, sint16le - signed 16-bit word (-32768..32767)
  sint32be, sint32le - signed 32-bit word (-2^31..2^31-1)

As of now, unsigned 32-bit words are not supported.

Keywords ending in "be" will cause the values to be written most significant
byte first ("big endian", aka network byte order) while those ending in "le"
will instead write the least significant byte first ("little endian", Intel
format).

The values to be written in binary must be numbers or vectors; the latter
will be written component by component as specified, in the standard x-y-z
order, without any separating or enclosing characters.

There is a sample macro called 'ARRAYS_WriteDF3' in arrays.inc which shows how
this feature may be used.

---------------------------------
Subsurface Light Transport (SSLT)
---------------------------------

Beta 31 adds experimental support for subsurface light transport (aka subsurface scattering).

Currently, SSLT is activated for a particular object by adding the following statement to
its finish (note that this is very likely to change):

  subsurface { COLOR, COLOR }

specifying the (reduced) scattering coefficients (sigma'[s]) and absorption coefficients
(sigma[a]), respectively, in units of 1/mm, for each of the three basic colors. The object's
IOR will also affect the results.

The algorithm is designed to give realistic results at a scale of 10 mm per POV-Ray unit by
default; for other scales, place the following statement in the global_settings section:

  mm_per_unit NUMBER

To tune the algorithm for quality or performance, the number of samples for the diffuse
scattering and single-scattering approximation, respectively, can be specified by placing
the following statement in the global_settings section:

  subsurface { samples NUMBER, NUMBER }

There is a sample SSLT scene in scenes/subsurface/subsurface.pov.

SSLT is still in alpha stage.

-------------------------------------------
Changes between 3.7.beta.29 and 3.7.beta.31
-------------------------------------------

Fixed inconsistent usage of int/long in line numbers within POVMS messages,
which caused warning messages in some cases to be printed without location
information.

Implemented filename display in console warning and error message output where
name is supplied from core code.

Changed windows progress panel to auto-size render progress bar such that it
will either fit in remaining status panel space, or not be shown at all. This
ought to resolve several reported issues where it overlaid the panel text.

Fixed bug that caused wrong radiosity illumination on transformed mapped textures.

Numerous fixes/changes for Unix autoconf/automake code, plus a number of bashism's
in scripts.

Major radiosity improvements, plus mosaic preview is now implemented: thanks to
new contributor Christoph Lipka for both of these.

Fixed Windows install issue where shortcut to SSE2 binary was always used even
if system didn't have SSE2.

-------------------------------------------
Changes between 3.7.beta.28 and 3.7.beta.29
-------------------------------------------

Allow POVWIN 'save as' to succeed without 'file is already open in editor'
error if case of current file is being changed.

Improved detection of true number of logical and physical cores on Intel CPU's.

Added colored text output to POVWIN message window. warning and debug messages
get different colors than error messages and standard text.

Added ability to declare an identifier as deprecated.

Many updates to scene and include files (see revision.txt for more details).

Worked around issue where new (for 3.7) crackle hash function returns large
range of possible values, causing memory used by cache to grow quickly. Work-
around is to revert to old hash function (this may also make crackle faster
since now we will get more cache hits).

Moved assumed location of POVWIN user-editable files into a subdir of 'My
Documents'.

Fixed two crashes reported in thread <web.48b1839e38b6f50ec03ef3130@news.povray.org>.

Fixed sphere_sweep parse crash reported in <web.48bc447cc2ccad1e8510f03f0@news.povray.org>.

Changed POVWIN UCS2 handling so that ASCII codes > 127 but < 256 are able to
be used. This should solve the issue reported in <48c04138$1@news.povray.org>.

Changed media confidence test to accept 0.0 as per docs.

Fixed crash in JPEG code.

Included Solaris patch by John Martin as reported in <web.47e9bdccd4b82d06c7064b8c0%40news.povray.org>.

  Deprecation Support
  -------------------

  The ability to add a 'deprecated' flag to a #declare has been added. This is
  to aid in migrating scenes away from old constructs (e.g. old textures). The
  usage is illustrated below:

    #declare deprecated Col_Glass_Old=color rgbf <0.8, 0.9, 0.85, 0.85>;
    #declare deprecated once Col_Glass_Old=... etc
    #declare deprecated "Some message" Col_Glass_Old=... etc

  A deprecated identifier generates no message at the time it is declared: a
  warning is only issued if it is used.

  If the optional 'once' keyword is present it must immediately follow the
  'deprecated' keyword and indicates that the warning should only be
  displayed once per parse.

  If the optional message string is present, it will be used as the warning
  to be displayed if the identifier is used. Otherwise, a message of the form
  "Identifier 'Col_Glass_Old' was declared deprecated." is used.

  An identifier is considered 'used' if it is referenced anywhere (even if in
  another #declare).

-------------------------------------------
Changes between 3.7.beta.27 and 3.7.beta.28
-------------------------------------------

Fixed multiple invocations of crash handler if exceptions occur in more than
one thread.

Fixed 'white outlines in df3 patterns with interpolate 2' issue reported in
  <483d2920@news.povray.org>.

Fixed str() crash reported in <web.4880f0adaf19f856c59235590@news.povray.org>.

Fixed bounding box calculation flaw that caused in some cases major slow-downs
  in scenes using difference (e.g. abyss.pov).

Re-implemented light color cache for textures. without this, each subsequent
layer (after the first) in a multi-layered texture will cause an unnecessary
call to TraceShadowRay and its subsequent intersection test to determine the
light color at that point.

Fixed issue with INI directory exclusion in IO permissions.

Improvements to Windows installer: now asks if install is for one user or all
users, and sets default install dir to suit. Note: it would be nice to detect
if a user has Administrator permissions prior to showing this option, but
unfortunately - at least on Vista - the windows installer engine intentionally
provides false information about the privileges of the user. This will lead to
non-privileged Vista users being offered the opportunity to do a global install
which of course will fail (presuming they accept the default destination). The
workaround for this (setting a property) causes the opposite problem: all users
get tagged as not having Administrator permissions, even if UAC elevation would
have granted it during install.

-------------------------------------------
Changes between 3.7.beta.26 and 3.7.beta.27
-------------------------------------------

Fixed incorrect flag test which would have resulted in issues with cutaway
textures and CSG or objects with double_illuminate set.

Fixed crash with inverse and CSG reported in <web.4828b51b6d261ebff3e4f6a20@news.povray.org>.

Added support for specifying grayscale output via INI file or command-line.

  This is intended to replace the use of hf_gray_16 in global_settings.
  hf_gray_16, if encountered, has no effect on the output type and will
  additionally generate a warning message (as before).

  Currently only PNG file support is provided with grayscale output; others
  will be added over time.

  Grayscale output may be specified via 'Grayscale_Output=true' as an INI
  option, or '+Fxg' (for output type 'x') as a command-line option. For
  example, '+Fng' for PNG grayscale output.

  Caveat: grayscale output implies the maximum bit-depth the format supports;
  for PNG this is 16. it is not valid to specify bits per color channel with
  'g' (e.g. '+Fng16' is not allowed, and nor for that matter is '+Fn16g'). If
  bits per channel is provided via an INI option, it is ignored.

Improved handling of memory allocation failures during parse.

Fixed issue whereby manual bounds, clips, patterns, UV, and interior were left
behind when a transformation was applied to a CSG object.

Changed back to using pvengine.ini to store POVWIN options and improved the
code that migrates version 3.6 options (if present) to 3.7. NOTE: not all
options from the v3.6 pvengine.ini are migrated: this is intentional and may
change later (it mainly involves options that contained pathnames).

Further split the POVWIN install and data dirs - this moves the ini, scenes,
and insert menu directories to the user's Application Data folder, for example,
c:\Documents and Settings\<user name>\Application Data\POV-Ray\v3.7\.

Created a Windows Installer which takes care of setting up the above for Win32
systems. Win64 is pending. NOTE: the installer currently only installs for the
user who ran it: that is, the 'Application Data\POV-Ray\v3.7\...' files are
only installed for that user. This won't be the case with the final installer;
it will set things up such that when pvengine.exe is run for the first time by
a user who has not had the program set up for them, the appropriate files are
created in their Application Data directory (this is a Windows Installer feature).

-------------------------------------------
Changes between 3.7.beta.25 and 3.7.beta.26
-------------------------------------------

Fix the "no_image and transparency" problem reported in <web.46f84a9cd032f3c7cb86afba0@news.povray.org>.

Fix the animation frame number issue reported in <478561e3@news.povray.org>;

Re-enable Include_Header thanks to patch from Stefaan De Roeck (see <47fb5d65@news.povray.org>).

Fix 'library path accumulation' issue reported in <481da512$1@news.povray.org>.

Apply isosurface cache fix suggested by Lukas Winter in <47c5b8b6$1@news.povray.org>.

Workaround for race condition that would cause 'timed out waiting for worker thread' error.

-------------------------------------------
Changes between 3.7.beta.24 and 3.7.beta.25
-------------------------------------------

Windows: moved all settings that used to be in PVENGINE.INI into the registry.
  This means that all PVENGINE settings (not to be confused with editor settings,
  which were already in the registry) will revert to their defaults. PVENGINE.INI
  is no longer used by POV-Ray 3.7.

Windows: moved the location of PVTOOLS.INI into the user profile folder: e.g.
    C:\Documents and Settings\<user>\Application Data\POV-Ray for Windows\pvtools.ini
  This change only alters the location that POV-Ray for Windows looks for the
  tools file - it does *not* automatically copy it. This is because of course
  when 3.7 is finally distributed, the installer will put the file in the
  correct place. If you use pvtools.ini, please manually copy it as above (the
  destination folder will be created the first time the new beta runs).

Windows: as of this beta, version 5 of the common control DLL is required.
  This was supplied with IE5, so it's highly unlikely that it won't be present
  on any version of windows that POVWIN still supports.

Linux: add auto setting of thread count and rework --benchmark. The number of
  threads is now set as the number of detected CPUs, or 4 otherwise. The built-in
  benchmark now accepts +Lpath command-line options and does no longer read any
  INI file but the provided one.

Fixed double-illumination problem with the area_illumination feature.

Fixed an issue where irid, ground fog, and constant fog were using noise generator
  0 rather than the default generator.

Fixed the 'area lights and transform' bug reported in
  <web.4639ad4565c782bbc717c9af0@news.povray.org>.

-------------------------------------------
Changes between 3.7.beta.23 and 3.7.beta.24
-------------------------------------------

Added multiple-thread support to photon shooting code. To take advantage
  of this at the moment, your scene will need multiple light sources.
Added experimental support for full area light diffuse and specular
  illumination. By default this is off and thus area lights will work as
  previously, but the new feature can be turned on by specifying the new
  'area_illumination' keyword (followed by an optional on/off keyword) in
  the light source definition. The settings which determine the quality of
  the lighting are the Size_1 and Size_2 parameters of the area light
  (similarly to how they determine the quality of the shadows).
Added experimental support for reading the pixel resolution of an image
  map. This is done by giving an image map pigment identifier to max_extent(),
  which will ten return the resolution of the image map as the x and y values
  of the returned vector.
Added a new list pattern type: 'cubic'. It takes six texture elements and maps
  each one to each of the six pyramids centered at each half-axis (thus
  effectively mapping each texture element to each side of a origin-centered
  cube).
Added a new warp type: cubic (which takes no parameters). It maps an area
  in the x-y plane between <0,0> and <1,1> around the origin in the same way
  as uv-mapping an origin-centered cube-shaped box would. (Naturally the warp
  works with any object whereas the uv-mapping only works for the box object.)
  See the documentation of box uv-mapping for details.
Fixed superellipsoid bug reported in <6p8nj3tckhrd1pihpofmvltqrfrs4lish8@4ax.com>

-------------------------------------------
Changes between 3.7.beta.22 and 3.7.beta.23
-------------------------------------------

POVWIN now allows an expired beta to be extended by up to one week at a time.
Photon refraction and dispersion fixes.
Added comparison ('=', '!=', '<', '<=', '>', '>=') support for strings.

--------------------------------------------
Changes between 3.7.beta.20b and 3.7.beta.22
--------------------------------------------

The trace level in the trace() function is now incremented only if
  an object was hit and the object is marked to increment the trace
  level, or if the ray was a radiosity ray. Objects which do not use
  reflection nor ior (but which might be semi-transparent) are marked
  as not incrementing the trace level.
Workaround for the temp file mapping not being completed.
  Temp files are now created as before (in the place specified).
Fixed issue whereby an I/O restrictions error would be displayed rather than
  'input file not found' in certain cases where POVWIN was asked to render a
  source file that was not present.
Further fix for media_attenuation bug
Fix SDL crash reported in <4617c41e$1@news.povray.org>.
Added Control-A support in windows version commandline input box (select all).
Changed windows version render window keypress code to hand focus to main window
  for any key, not just escape.
Fixed fog (and participating media) shadow attenuation issues.
  Media computation was ignoring the lightsource's media_attenuation
  flag under some circumstances, and was attenuating shadow rays if
  the shadow ray had intersected an object.
Fixed jpeg temp file issue reported in thread <web.46168c053403448a4f02351a0@news.povray.org>.
Fixed incorrect unix exit value when closing the display window (user abort)
Temporarily hard-coded INI keywords into editor syntax table for INI files.

Changes between 3.7.beta.20a and 3.7.beta.20b
---------------------------------------------

Added 'alternate render file' feature to povwin IDE. See comments below.
Added extensions .MCR and .MAC to list of files povwin considers include
  files (i.e. which are filtered as such in the various file dialogs and
  assigned the POV file type for the editor syntax highlighting).
Added .INI file type to povwin editor syntax highlighting.
Added window menu to povwin IDE. Entries are MRU-sorted.
Activated memory statistics code in Windows build.
Fixed issue with editor window splitting not being restored
  (<45620b9e$1@news.povray.org>).
Fixed issue with file type not being set on initial save if 'save as'
  was not used (reported many times, including <45602a08@news.povray.org>
  and <46092c8a@news.povray.org>).

  Windows Editor Changes
  ----------------------

  This beta introduces two notable changes to the POVWIN IDE.

  Firstly, it now has a Window menu, which is located where the GUIEXT
  menu used to be (the latter has moved to within the Options menu).

  While technically a Window menu is not necessary, as all open files
  are visible in tabs, the addition of this menu provides two advantages:

    1. We can provide the option of showing all tabs on a single line,
       with a scroller to view non-visible ones. This has not yet been
       added but will be at a later point.

    2. The MRU arrangement of the window menu makes it trivial to toggle
       between files without taking your eyes off the text or using the
       mouse. The most recently view window (i.e. the current one) will
       always be entry 1 in the list. The second most recently viewed
       (i.e. the last window viewed before switching to the current one)
       will always be entry 2 in the list, and so forth. Given that
       entries 1 through 10 in the list are given the menu mnemonics
       1 through 0 respectively, it is therefore clear that to toggle
       between the current and previous files all you need to do is hit
       Alt-W then 2. To go to the third oldest, Alt-W then 3, and so
       forth.

       Currently, the MRU list is not saved on exit. This will be added.
       We may also add keyboard accelerators (e.g. ALT-2, ALT-3 etc) as
       a shortcut for Alt-W 2, etc.

  Secondly, there is now an 'alternate render file' feature. This is
  intended to make things easier when editing macro or include files.
  While it is possible to use SDL to detect whether a macro/include file
  is being rendered directly and to pull in supporting code, that approach
  is not very flexible.

  The alternate render file feature allows a render to be started on an
  include file, and instead of the include file being rendered directly
  (as would have happened previously), the source file that most recently
  included that file in a render will be rendered instead. Note that by
  'source file', we mean either a .POV or .INI file.

  For this feature to work, you need to have rendered a file which
  includes the target file during the current editing session (the
  association between include files and source files is not persisted when
  POVWIN exits). Additionally you need to have requested to render a
  source file which does not have the .POV or .INI extension. When you
  request the render, a message box will appear asking you what to do. You
  can choose to render the alternate file this time only, to render the
  alternate file each time you render this one, or to render this one each
  time (i.e. disable the alternate file option).

  In all cases, the choice you give only persists for the current editing
  session; it is not restored when you re-launch POVWIN. This is by
  design.

Changes between 3.7.beta.20 and 3.7.beta.20a
--------------------------------------------

Added preliminary Linux support for CPU timer; might return incorrect results
   depending on the platform.
Added preliminary Linux support for signal catching (e.g. when aborting a
   render by hitting Ctrl+C).
Fixed the +p option under Linux to trigger an interframe pause in animations.
Fixed unrestricted display and file gamma; must now be at least 0.001.
Fixed PNG gamma issue reported in <45aa976e$1@news.povray.org> and
   <45c11eed$1@news.povray.org>.
Fixed uv mapping issue reported in <45602a08@news.povray.org> and
   <46092c8a@news.povray.org>.
Fixed Winpov issue with editor window splitting not being restored
   reported in <45620b9e$1@news.povray.org>.
Fixed Winpov issue with file type not being set on initial save if 'save as'
   was not used (reported many times, including <45602a08@news.povray.org>
   and <46092c8a@news.povray.org>).
Fixed exit code for the Linux build; now 0 = ok, 1 = error, 2 = user abort.
Tweaked a few scene files.
Improved w3c conformance and keyword index for the Linux docs.

Changes between 3.7.beta.19 and 3.7.beta.20
-------------------------------------------

Added 'file modified' indicator to filename shown in POVWIN main window
  caption.
Added feature notification for when auto-reload results in files being
  auto-saved.
Some vfe changes to assist resolution of the 'pause after render' race
  condition.
Added support for --benchmark on unix (works together with +wt) and print
  built-in features with --version

Changes between 3.7.beta.18 and 3.7.beta.19
-------------------------------------------

Fixed render never completes when using crackle error reported in
   <web.458d0fbb495005281bd6cd0c0@news.povray.org> and several others.
Fixed issue reported in <45781d0d$1@news.povray.org> where reading a
   continue state file would hang POV.
Fixed "POV-Ray reports wrong file to be missing" Unix issue reported in
   <pan.2006.12.30.10.45.30.743879@removeit.geloescht.net>.
Fixed a minor issue with #version handling as found in the Linux betas.

Changes between 3.7.beta.17 and 3.7.beta.18
-------------------------------------------

Added preliminary support for per-thread crackle pattern cache.
Fixed a povwin bug in vidcap code.
Added experimental windows-specific memory management code.
Improved the Unix preview display code.

Changes between 3.7.beta.16 and 3.7.beta.17
-------------------------------------------

Unix default file gamma changed from from 1.0 to 2.2.
Fixed crash reported in <web.453677b9876cd74e72d86b490@news.povray.org>.
Fixed issue with trace returning an incorrect intersection point in some
  circumstances (see <web.45367d932f1ac4de72d86b490@news.povray.org>).
Fixed issue caused by failure to clear ray interiors during focal blur sample
  loop (<web.45424a798f1b3f6c1bd6cd0c0@news.povray.org>).
Added RTR (real-time raytracing), clockless animation, and video capture
  support (windows only). See below for more information.
Fixed bug that stopped radiosity from being activated when it should have been.
Enabled multi-threaded radiosity. This is still VERY experimental and is in no
  way in its final form.
Fixed missing definition for FILENAME_SEPARATOR that caused run failure with
  absolute filenames on unix systems.
Fixed infinite loop in radiosity pre-trace code that would occur with small
  values of pretrace end.
Fixed issue with BSP missing objects and speckled rendering (cornell.pov gave
  a good example of both).
Improved BSP tree build speed; it is now roughly twice as fast on complex
  scenes (e.g. isocacti.pov).
Fixed 'Subset_Start_Frame not working' issue
  (<web.454b67a8defacc9bf2985afc0@news.povray.org>).
Fixed issue with sys output file extension on windows
  (<455a0770@news.povray.org>).
Improved povwin vidcap handling of video source pins that are not RGB8 (it
  now ignores them).

  Real-Time Raytracing
  --------------------

  POV-Ray now has some highly experimental support for a real-time raytracing
  loop. This is basically a mode where a single pre-parsed scene is rendered
  multiple times with no re-parsing inbetween frames. The camera is moved
  according to camera definitions provided in the main scene file. Additionally,
  on windows, a live video stream (e.g. from a webcam) may be mapped into the
  image in exactly the same way that a normal image map may be.

  For full documentation on these features, please see http://www.povray.org/beta/rtr/.

Changes between 3.7.beta.15 and 3.7.beta.16
-------------------------------------------

Work around an issue caused by apparent resource starvation within windows.
  This would show itself as non-updating editor windows when switching tabs
  or focus.
Added support for 'pause when done' in linux build.
Changed alpha handling when version is set to 3.7 (see below).
Fixed animation problem where Initial_Frame was ignored.
Changed WorkThreads INI option to Work_Threads for consistency.
Changed bounding method command-line option from +b2 to +bm2 for the same reason.
Fixed major slowdown when using BSP bounding, an orthographic camera (or
  any camera with non-constant origin), and large numbers of slow objects.
Added ability to close edit tab in windows version by middle-clicking on it.
  (NB this means on the tab itself, not the contents of the tab).
  Also, Ctrl-W now defaults to closing the current editor file.
Improve parsing of POVWIN-specific command-line filenames containing single
  quotes.
Added /EDITDLLPATH command-line parameter which overrides the default
  edit DLL locations for the windows version.
Added SEH and minidump generation to windows code. After an unhandled exception
  POVWIN will now offer the option of creating a minidump (brief or full) for
  submission to the team to assist in tracking down crashes.
Changed default number of threads in windows version to number of CPU's
  (was number of CPU's * 2).

  Photon Changes
  --------------

  We are re-working some areas of the photon support, and as such photons will
  not work as well as in the previous beta.

  Alpha Changes
  -------------

  Some changes have been made to the way alpha is handled when +UA is activated.
  Firstly, in previous versions, specifying a background with the background
  keyword would by default supply a background with transmit set to 1.0 (i.e.
  fully transparent provided that +ua is being used). This is no longer the case.

  While the default background is transparent, any background specified in a
  scene file (unless 3.6 or earlier compatibility is being used) will now be
  opaque unless transmit is explicitly given. (In other words, use rgbft<>
  rather than rgb<> in the background statement if you want the old behaviour).

  Secondly, the way that objects are blended with the background has changed.
  Previously the color of the background was not taken into account when
  calculating effects of transmission through translucent objects when +ua is
  in effect (i.e. where the background could otherwise have been seen through
  the object). Now, however, the background color is taken into account, even
  if it is not otherwise visible. (In other words, blending is performed in the
  same way regardless of the presence of background transparency).

  Note that this change is not affected by the #version directive, so it may
  change the appearance of scenes written for version 3.6 and earlier. We will
  monitor feedback on this from beta testers to evaluate the impact of this.

Changes between 3.7.beta.14/14a and 3.7.beta.15
-----------------------------------------------

Fixed PNG output causing corrupted (yet often readable) files
Fixed broken RLE Targa output (+FC) causing program abort
Partial fix for "Crash when assigning materials" issue reported in <44f596fa$1@news.povray.org>
Partial fix for "Darkness in grenadine.pov" issue reported in <web.448348adc379ad5b1bd6cd0c0@news.povray.org>
Fixed large DF3 files issue reported in <web.44f40e4698b0d9e4b399450c0@news.povray.org>
Fixed legacy heap overwrite in BVH code reported in <web.44e5a00bfcc26e0fc717c9af0@news.povray.org>
Added ability to specify thread count from Windows version render menu (unsaved setting)
Fixed Linux "Unknown internal error" issue reported in <44fc07af$1@news.povray.org>
Improved html code and navigation for the Linux documentation

Changes between 3.7.beta.13 and 3.7.beta.14
--------------------------------------------

Added radiosity on/off flag for objects
Fixed default blend map destruction issue
Fixed photons with media issue
Added "WorkThreads" INI option and "WT" command-line option
Added "File_Gamma" INI option
Added gamma correction to file output
First beta release for Linux

Changes between 3.7.beta.12a and 3.7.beta.13
--------------------------------------------

Some fixes to bounding and object count statistics.
Fixed render percentage error when a large number of pixels are being rendered.
Parse and bounding times are now included in stream output.
Implemented debug output to stream.
Bugfix for printing of max depth stopped nodes per node.
Improved error reporting when exception is caught in renderbackend.
Fixed sombrero.pov bug reported in <web.442c3cd3ccb62fd8c7294af50@news.povray.org>.
Fixed issue with ray interior being removed during evaluation of area lights.
Fixed issue with intersection min depth being too coarse (e.g. the liquid in
  the glass in balcony.pov did not render).
No longer send mem usage stats as they are not accurate (will restore this before
  final release).
Fixed photon memory issue referred to in <web.444b4f4ed5b924f08b9c27240@news.povray.org>.
Fixed object count when no bounding is used, rendering empty file leaves stop icon, and
  winpov exit command not working issues as reported in <442df1da$1@news.povray.org>.

Changes between 3.7.beta.12 and 3.7.beta.12a
--------------------------------------------

Fixed issue with BSP that caused long build times on large trees.
Changed default BSP child access cost to 5.0 (was 1.5).
Fixed issue with BSP trees that would cause some objects to vanish.
Added an optimization which speeds up BSP renders.

Changes between 3.7.beta.11c and 3.7.beta.12
--------------------------------------------

Fixed spheresweep copy bug reported in <43fbaf97$1@news.povray.org>.
Fixed 'aa incorrectly reported to be on' issue reported in <43fc75f9$1@news.povray.org>.
Added progress and stats reporting for BSP bounding.
Fixed camera inside media/interior mostly lost bug.
Fixed debug message output.
AA method 1 block artifact fix (<43ebe0bc@news.povray.org>). Also correct
  some jitter option issues. NB it is still technically possible that
  block-boundary AA artifacts could occur but they are much less likely.
Fixed bug in generation of lit intervals for media.
Fixed "light doesn't pass through transparent image_map" issue
  (<43a97c75$1@news.povray.org>).
Fixed 'trace fails with no_image object in union' bug
  (<43f57a9d$1@news.povray.org>.)
Fixed issue where cancelling a render may not work if all CPU resources
  are committed to the render.
Fixed 'unrecognized file format' warning when HDR output is selected.
Fixed flipped image HDR reading bug (<43e8190e@news.povray.org>)
Fixed one dispersion bug (long render times).
Re-implemented display retention and bitmap preservation during animation.
Added fix for image filename generation and rendered pixel counting.
Fixed gamma assignment in PNG output.

  Render Window
  -------------

  Due to issues with CPU usage, the new render window is now by default
  off. To work well this feature requires that hardware-assisted alpha
  blending is available on the target system, and as of the time of writing
  this is not common enough to justify turning it on by default.

  Note: it will remain turned on if you already had it on (e.g. from a
  previous beta).

  BSP Bounding
  ------------

  BSP (Binary Space Partitioning) tree bounding is now available. To turn
  it on use '+B2' or 'Bounding_Method=2' in the INI file or on the command-
  line. When it is in use you will get some additional statistics in the
  output pane regarding the built tree.

  Please keep in mind that this implementation of BSP is highly beta and
  will not speed up scenes in many cases (and in fact may slow some down).
  In particular the building of the tree can take a long time and lots of
  memory in severe cases. Using the BSP tree rather than our traditional
  BVH system (default or +B1) is a choice best made for specific scenes
  that will benefit from the way the BSP operates, and in particular if
  the render is long enough to offset the build time. (The BSP tree build
  time will be constant for a given scene and set of BSP parameters,
  regardless of the output resolution. A 30-second BSP build may not be
  a good choice on a 60-second test render but may be acceptable for a
  60-minute final render if the use of BSP adds a few PPS).

  On some scenes the difference however will be dramatic, with short
  build times and radically increased render speed.

  We have provided some BSP-related options via the INI file and encourage
  you to experiment with them to see if you can get better results than
  the default values built in to POV-Ray. We will listen to feedback from
  this and if necessary tweak the defaults. We do not guarantee that all
  of the following INI file settings will remain in the final release of
  3.7.

    BSP_MaxDepth=128
    BSP_BaseAccessCost=1.0
    BSP_ChildAccessCost=1.5
    BSP_IsectCost=150.0
    BSP_MissChance=0.2

  The values shown above are the default. You can also get the defaults
  if you use a value of 0 for any of the above (or of course just by not
  specifying the option at all). For an explanation of what the values
  mean you may refer to Ray Tracing News v17n1 (look for Eric Haines'
  article on BSP), or follow the discussion on BSP that is sure to crop
  up in the beta-test group.

  Please note that we are aware of some render artifacts visible with +B2
  and are seeking to address them. Don't be surprised if you find some,
  and if you can generate a minimal scene demonstrating them feel free to
  post it to the appropriate group.

  Example BSP scene
  -----------------

  There is a scene included with this release called 'Tango.pov' which is
  a good example of a scene that benefits from the BSP bounding.

  Tango.pov rendered at 800x600, no AA -

    With +B1 : 70 seconds total
    With +B2 : 48 seconds total

Changes between 3.7.beta.10 and 3.7.beta.11c
--------------------------------------------

No core bugs have been fixed. This release extends the expiration time
to the start of April 2006 and provides a new render window feature.

  Render Window
  -------------

  The new render window mode is only available on Windows 2000 or later.
  The presence of this code may case the beta to be unable to load on
  Windows 9x systems; if this occurs it will be fixed in the next beta.
  Note that we have not tested this new code on a Windows 2000 system,
  so we can't comment on how well it will work on those systems.

  To activate the new render window, open the 'Render Window' sub-menu in
  the 'Options' menu, and select the 'Use New-style Render Window' entry.

  The new render window is designed to help users get around the issue of
  the render window getting in the way when doing edit/render/fix cycles.
  It supports a 'transparency' mode that is in effect two things: both
  optical transparency (or more specifically translucency), and input
  transparency (more specifically, the Windows WS_EX_TRANSPARENT style).

  'Input transparency' means that the window is transparent to input -
  so if you move your mouse over it or attempt to click on it, the mouse
  messages are in fact sent to whatever is underneath the window. In
  effect therefore it is as if the window were not there - even if you
  can still see it.

  The effect of this is that, coupled with translucency, you can both
  see what is under the window (e.g. the POV-Ray editor), and also work
  with it (typing or selecting with the mouse, etc).

  'Input Transparency' is enabled whenever you set the translucency of
  the render window to 25% or more (see below). At settings less than
  this, the render window will behave more or less as normal (though
  without some of the features of the classic render window, such as the
  ability to be de-coupled from the main window such that it does not
  get hidden when the main window is minimized).

  To set the translucency of the render window, either rotate your mouse
  wheel when the render window has focus (this is the preferred method),
  or alternatively right-click on the window's title bar and choose a
  setting from the context menu that is provided.

  When the render window has input focus, translucency is removed and it
  becomes opaque. It will switch back once another window gets focus, or
  if you adjust the translucency using one of the above methods.

  If you want to work with input transparency, it is important that you
  understand that this means you can't work with the render window in
  the manner you are accustomed to, since of course the window will pass
  input to the application below it. To allow for interaction with the
  window in this circumstance, we have added a feature whereby hovering
  the mouse over the render window's caption for a short time, or clicking
  on the title bar, will activate the window, make it opaque, and allow
  input to be processed normally.

  (Of course the ability to click on the caption means that it's not
  completely input transparent, and we might disable this feature later
  if the hover feature works out well).

  You will know if your mouse is over the appropriate area of the window
  since the cursor will turn to a hourglass shape during the 'hover' time.

  Provided that the window is left in input transparency mode, if you
  move your mouse out of the window for a short time, it will automatically
  snap back into its former translucent mode.

  You can tell if the window is in input transparency mode by looking for
  a '[T]' at the start of the render window caption. If present, then it's
  going to pass input to the application underneath it. While adjusting
  the translucency with the mouse wheel, the caption will display the new
  translucency setting and, if appropriate, a comment that the window has
  switched to passing input. (Recall however that this doesn't kick in
  until you switch focus to another window).

Changes between 3.7.beta.9 and 3.7.beta.10
------------------------------------------

Added gamma correction support.
Add more frequent stop-checking to all render tasks.
Radiosity now works a lot better than beta.9.
Fixed some memory leaks in radiosity.
Fixed crash in some image file reads.
Improved handling of cancel render in windows version.
Fixed output filename generation logic.
Changed all internal file paths to UCS2.
Fix for using truetype in CSG.
Improved responsiveness in backend.

  Gamma Correction
  ----------------

  The way POV-Ray 3.7 handles the 'assumed_gamma' keyword has changed.
  Previously the presence of this keyword in global_settings caused a
  'possible error' warning and its presence was ignored. In addition
  no gamma correction was available in previous betas. Starting with
  beta.10 however, gamma correction is performed on both the display and
  file output, subject to the following criteria:

    o If the scene language version is set to 3.7 (or not set at all), then
      gamma correction will default to ON, with the value used being set by
      the 'display_gamma' INI file setting. Note that in previous versions of
      POV-Ray gamma correction was OFF by default but otherwise this is the
      same.

    o If the scene language version is set to earlier than 3.7, then gamma
      will be OFF by default.

    o Notwithstanding the above, if the keyword 'assumed_gamma' is present
      in the scene's global_settings, then POV will take one of the following
      actions:

        a) if "assumed_gamma 2.2" is present, gamma correction will be turned
           OFF and a warning issued. the same thing will happen if the value
           specified is not 2.2 but happens to be the default for the platform
           setting given to POV-Ray when it was compiled (e.g. Windows is 2.2).

        b) if "assumed_gamma 1.0" is present, gamma correction will be turned
           ON (if it's not already on) and in any case a warning will be issued.

        c) if a value other than the above is specified, it is ignored and a
           'possible error' message is issued.

      You will note from the above that therefore it is no longer possible to
      adjust the amount of gamma correction from a scene file. This is as
      designed since scene files should be as much as possible be platform
      independent, and the gamma of particular display hardware does not belong
      in the scene file. If you really need to specify 'assumed_gamma' you can
      do so in an INI file or on the command-line; however in those cases you
      may as well just use 'display_gamma' in its place.

      When writing file formats that support gamma specification, the inverse
      of the assumed_gamma value will be embedded in the file headers, so that
      an appropriately equipped display program can 'undo' the gamma correction
      if it is so desired. This is as per previous versions of POV-Ray.

  Frontend and Backend
  --------------------

  Note that POV-Ray uses a logical separation of frontend and backend. The
  'frontend' is that part which deals with the user-interface, locating files,
  parsing command-line options, reading INI files, and so forth. The 'backend'
  deals with parsing the scene file and doing the actual render. These two parts
  of POV-Ray communicate via a message-passing interface, even when linked into
  the one executable program.

  Whilst currently not supported, it is entirely possible to separate the front
  and back ends via for example a network interface, and have the render done
  on one machine while the user interface (and display) is on another. Knowing
  this may make it easier to understand why, for example, we are moving away
  from allowing things such as gamma correction to be specified in the scene
  file; there is no reason to assume the scene file is on the same machine as
  the image will be displayed upon, and as such the specification of gamma
  should be done in the frontend via INI or command-line options.

  There will be more changes along these lines as we prepare for the future
  transition to a fully network-capable renderer. The POV-Team will attempt
  to ease the change to the new system by doing things such as the assumed_gamma
  interpretation above, where it is possible to do so.

Changes between 3.7.beta.8 and 3.7.beta.9
-----------------------------------------

Fixed crash caused by resource exhaustion (too many threads); refer <4303d267$1@news.povray.org>.
Addressed state issue referred to in <web.42af2f04951c51e46a3607400@news.povray.org>.
Fixed output file reporting issue reported in <web.430dc75ff23d654e726bd13c0@news.povray.org>.
Fixed AA method 2 crash reported in <430358ed@news.povray.org>.
Fixed render window re-display problem.
Fixed focal blur problem.
Moved assumed_gamma to command-line or INI-file only option (causes warning if found in scene).

  Render block size
  -----------------

  You now have the ability to specify the render block size via either an
  INI-style option ("Render_Block_Size=n") or on the command-line ("+BSn"),
  where 'n' is an integer larger than or equal to 4. This represents the
  edge size of the square used to distribute work to the render threads,
  and thus the number of pixels in each block will be n squared.

  The default value is 32. If you specify a value that is greater than the
  larger of the width or height of the image being rendered, it is clipped
  to that value.

  Note that using render block sizes of less than eight can impact performance,
  particularly on large images that render quickly, as it significantly
  increases the amount of message traffic between the render backend and the
  graphical frontend (which communicate using a shared-memory queue).

  Editor
  ------

  A few changes have been made to the editor in the hope of avoiding the
  error that some users get when it attempts to open a file that has been
  removed from the disk. We have not been able to replicate this error
  ourselves (the code was already designed to handle this situation) so we
  have added some extra checks. The net result of this is that when a file
  no longer exists, instead of opening a blank file, the edit session for
  that file will instead be discarded.

  Additionally we have improved the handling of modified files during active
  application changes; now, you should never get more than one message box
  displayed at any one time (which previously could happen if you switched
  focus multiple times).

  Dispersion
  ----------

  Dispersion has been added back, however this is still mostly untested.
  There will be numerous issues with this; we would appreciate help in
  identifying what they are and where they may lie (i.e. reports that
  'dispersion doesn't work properly' with no additional information will
  not be of much help).

  Radiosity
  ---------

  Radiosity has been re-enabled. Currently it is limited to a single thread
  and has some issues. As stated for dispersion, we would appreciate assistance
  in determining where individual issues lie and what influences them.

  Multi-thread support will be added later, once the radiosity code settles
  down and is functioning as expected in single-thread mode.

  Mosaic Preview
  --------------

  Mosaic preview now works again. The same issue as mentioned in the above
  section on render block size apply; we don't recommend using an end preview
  size of less than 8. Note that unless you specify an end preview size the
  code will default to using +ep2, so it is strongly recommended that you
  do provide it.

  Be aware that when using mosaic preview, the count of rendered pixels shown
  in the status bar will be wrong. This will be fixed later.

  Improved handling of large render sizes
  ---------------------------------------

  Handling of large renders (e.g. 10,000 x 5,000 pixels) has been improved.
  Previously the intermediate data structure used to store rendered pixels
  was held in RAM. On windows it is now stored in a virtual-memory backed
  file which maps to the swap file. This means that your swap file needs to
  have at least enough free space to store this file at the start of a render.
  For reference, the amount of room needed is roughly 20 bytes per pixel, so
  the above example 10,000 x 5,000 pixel image would need one gigabyte in the
  swap file.

  One other issue to be aware of is that, on windows, there has to be enough
  contiguous virtual address space available to hold the file. This can be a
  problem since by default many Win32 systems only provide each process a total
  of two gigabytes of address space, which is then divided up amongst the
  exe and its various DLL's, the local heap, stack, and so forth. Additionally
  some Win9x versions (at the least Windows 95) will only allow a maximum of
  one gigabyte to be mapped in this way, and that is divided up amongst other
  resources as well.

  Therefore it is entirely possible that even if you have sufficient swap space
  the allocation of the memory mapped file will fail, at least for win32 users
  (win64 won't have this problem). We are working to fix this limitation by
  moving to a less efficient but more reliable file-based solution.

  One final note: please be aware that the Windows process manager will add the
  amount of virtual memory mapped by a process in this way to its total memory
  statistics. Please don't assume that the figure reported by Windows is
  necessarily the amount of physical RAM being used.

Changes between 3.7.beta.7 and 3.7.beta.8
-----------------------------------------

AA buffering restored; AA should be as efficient as version 3.6 now.
Fixed major problem in crackle when using more than one thread.
Reverted to older version of Intel compiler to avoid some optimization bugs.
Added HDR file support (RGBE, as used in Radiance).
Added EXR file support using OpenEXR library (http://www.openexr.org/).
Fixed animation clock jump issue.

Changes between 3.7.beta.6 and 3.7.beta.7
-----------------------------------------

New thread-safe random number generator added.
Continue trace support added (see release notice for usage details).
Animation support added.
Made render cancellation more responsive when large numbers of threads are in use.
Fixed most wrapping problems in windows message display.

Changes between 3.7.beta.5a and 3.7.beta.6
------------------------------------------

Fixed quadric bounding problem.
Fixed CSG merge problem.
Made numerous other changes to speed up code, should be closer to v3.6.1 now.

Changes between 3.7.beta.5 and 3.7.beta.5a
------------------------------------------

Fixed bug reported in <428de855@news.povray.org> re:sunsethf.pov.
Worked around SMP bug in trace related to lighting code altering lightsources during render.

Changes between 3.7.beta.4 and 3.7.beta.5
-----------------------------------------

Fixed a photon building issue that caused progressive slowdown.
Fixed scattering media problem reported in <427ca163@news.povray.org>.
(This also fixes <427c0121@news.povray.org>).
Parser now honors Split_Unions and Remove_Bounds options.
Fixed lathe artifacts bug reported in <427c0f95@news.povray.org>.
Fixed no_image and no_reflection issues reported in <427c1900@news.povray.org>.
Fixed area light orient issue reported in <427c14ef@news.povray.org>.
Fixed issue where a new clip statement would overwrite a previous one rather than appending to it.
Fixed speed issue with quadrics by reverting to old bbox calculation method.
Fixed a swathe of memory leaks.

Changes between 3.7.beta.3 and 3.7.beta.4
-----------------------------------------

Fixed indexed PNG alpha problem reported in <42765ef3$1@news.povray.org>.
Fix area light problem reported in <427a3fa5$1@news.povray.org>.
Fixed crash during trace of lathe reported in <42796797@news.povray.org>.
Improved handling of cancel/pause render.
Fixed max_trace_level calculation and display (see <42769105@news.povray.org>).
Fixed image memory leak.
Fixed speed issues reported in <42769f6d@news.povray.org>.
Fixed shadow problem mentioned in <42769f6d@news.povray.org>.
Fixed sphere_sweep bug reported in <42773e51@news.povray.org>.
Fixed 'inverting pre-declared union' crash reported in <42769b59@news.povray.org>.
Fixed focal blur issue.
Fixed omnimax camera bug reported in <42775c1b$1@news.povray.org>, plus several other related camera issues.
Fixed facets pattern crash reported in <42773fab$1@news.povray.org>.

Changes between 3.7.beta.2 and 3.7.beta.3
-----------------------------------------

Partial render (start col/row etc) now works
Fixed CSG merge issue reported in <42645c3b@news.povray.org>.
Added warning and better progress reporting to photons.
Some hollow media fixes.
Re-enabled alpha display in render window for windows port.
Fixed alpha bug reported in <web.426402d627a031d914107e060@news.povray.org>
Fixed no_image bug reported in <web.426402d627a031d914107e060@news.povray.org>
Changed default bounding threshold back to 3 as per v3.6.
Fixed alpha inversion bug in BMP, Targa, and PNG file reading/writing.
Fixed crash mentioned in <42689685@news.povray.org>.
Fixed noise generator default issue reported in <426898db@news.povray.org>.
Fixed irid problem reported in <42680b39@news.povray.org>.
Fix for area light problem from Massimo Valentini.
Made quick_colour work as it should.

Changes between 3.7.beta.1 and 3.7.beta.2
-----------------------------------------

CSG should now work properly
Problem with too many recursions when rendering shadows fixed
I/O restrictions should now work
Fixed recursion bug in renderer
Initialise photon variables
Restore ability to open error file in editor (note: column number not always correct).
Fixes no-display crash
Fixes image closing bug
Tweak to some radiosity local vars
Fixes rendering area bug
Fixes AA method 2 brightness issue
Add output file type '+FB' (bmp).
Add 'bmp' token to parser.
Fix for BMP reading.
File output defaults to on.
Fix render quality options output.
Change references to 'CPU(s)' to 'thread(s)'.
Update render time output to include fractional seconds.
Fix crash reported in <4263125b@news.povray.org> and one related bug.

Intentional changes for POV-Ray 3.7
-----------------------------------

The version directive and command-line setting no longer provide compatibility
with most rendering bugs in versions prior to POV-Ray 3.5. However, compatibility
with the scene language is provided for scenes as old as POV-Ray 1.0 just as
in all previous versions of POV-Ray. Nevertheless, we strongly recommend you
update scenes at least to POV-Ray 3.5 syntax if you plan to use them in future
versions of POV-Ray.

This version uses multi-threaded rendering by default. The ability to render
in more than one thread is primarily of use to those users who have SMP
machines (i.e. more than one CPU). There have been reports of benefits for
users of hyperthreading systems, particularly with higher thread counts (e.g.
16 threads).

You can render in only one thread by using the '/THREADS 1' switch in the
Windows version. Note that parsing and photon building will only use one
thread no matter how many are specified. However photon scenes will benefit
from multiple threads once photon building has completed.
