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Introduction

These release notes describe significant changes and enhancements to the RenderMan® Toolkit for the 11.3 release over the 10.0 release.

• Release Notes Since 11.0
  Fixes in the renderer between 11.0 and 11.3
• Ray Tracing and Indirect Illumination
  PRMan now supports ray tracing, indirection illumination, photon maps and more!
• Combined Shading
  PRMan now combines similar objects before shading, significantly speeding up scenes with many small objects.
• Tentative Hiding
  PRMan now aggressively resolves visibility prior to shading.
• Eyesplit Improvements
  Improvements have been made to the handling of eyesplits.
• Curve Optimizations
  Optimizations have been made to Curves to support the rendering of complex hair scenes.
• Deep Shadow Maps
  PRMan now supports deep shadow maps.
• Shadowmap Improvements
  The renderer has improved handling for shadow maps with large constant regions, and improved filtering leading to better quality shadows.
• Micropolygon caching
  PRMan can now cache to disk micropolygons which will be needed for sampling later, reducing the memory overhead necessary to store them.
• Subdivision Mesh Stitching
  PRMan can now stitch together subdivision meshes to ensure that no holes appear between seams.
• Double-sided Shading
  Two-sided primitives can now be shaded differently on each side.
• Shader Profiling Images
  You can now create images which allow profiling the cost of shaders.
• New Cross Platform Shading Language Preprocessor
  You can now count on a uniform RSL preprocessor across platforms. Complete with support for C++ style comments.
• Non-Raster Oriented Dicing
  Non-raster oriented dicing has been implemented for other geometry types.
• Hider Motion Sampling
  Motion sampling can now be disabled in the hider.
• Miscellaneous Changes and Bug Fixes
  Many parts of the release have had small changes and bug fixes.
• Limitations
  Known limitations in the current release.

Combined Shading

The renderer now has the ability to shade several geometric primitives at the same time, provided that you follow a few simple rules when writing shaders. If you follow these rules, small objects such as leaves, grass blades, hairs, pebbles, etc. will shade up to 4-5 times faster (in the limiting case where the objects are far away, and are diced into a single micropolygon each). This can speed up the overall rendering times for complex scenes by up to a factor of 3. Even in moderate cases, where individual objects turn into 20 or 30 micropolygons each, your shaders can execute up to twice as fast.

Tentative Hiding

PRMan 11 now attempts to resolve visibility in its entirety before shading. In nearly all cases this causes a frame to render faster. Only in the case of displaced geometry will PRMan 11 maintain the old behaviour, and in this case hiding can be controlled via a new Hider "occlusionbound" parameter.

Eyesplit Improvements

PRMan no longer discards primitives that reach the eyesplits limit. Primitives that reach the eyesplits limit are split further by a threshold value (controllable by an option), and then immediately diced. This can result in decreased image quality (and a warning to this effect will be issued), but typically leads to much better results than the old behavior of discarded geometry.

Curve Optimizations

A new Attribute for curves makes thin hair-like curves much cheaper to shade, and more memory efficient especially when spanning multiple buckets:

Attribute "dice" "hair" [1]

This attribute should only be used for curves which are truly hair-like (very thin in screen space).

Deep Shadowmaps

Support for "deep shadowmaps" has been added. This new output format stores more information per pixel than a normal shadowmap, and thus allows for better antialiasing, semi-transparent shadows, and limited cases of motion blurred shadows when used instead of normal shadowmaps.

Creation of these new shadow files is achieved with a new display driver, deepshad, while the shadow() shadeop has been upgraded to support deep shadow maps directly. 

Shadowmap Improvements

The renderer now significantly optimizes for the case of shadow maps which contain large empty regions.

The renderer now has improved filter behaviour when making shadow map calls. This may result in significantly different shadows between PRMan 10 and 11 (this is most noticeable when making 4-point shadow() calls) , but should lead to fewer self-shadow artifacts and better looking shadows.

Micropolygon caching

Previous versions of PRMan tried to prevent the number of micropolygons resident in memory from growing too large. In particular, the extreme displacement strategy was employed; however, while it was effective at reducing the memory footprint, extreme displacement resulted in redundant shading computation and longer render times.

Version 11.0 of PRMan now provides a new strategy: it will cache transient micropolygons to disk when it is detected that there are a relatively large number of them. By default, caching is activated once more than 6MB of transient micropolygons have been created.

Micropolygon caching can be controlled through several new hider options.

Subdivision Mesh Stitching

PRMan 11.0 allows two subdivision surfaces to be joined together seamlessly along a shared boundary curve, in order to ensure that no holes appear between seams even under extreme deformation or displacement. More details are provided in the user manual.

Double-sided Shading

Two-sided primitives can now be shaded twice, once on each side, using the new Attribute "sides" "doubleshaded".

Shader Profiling Images

A new variable that can be used in conjunction with arbitrary output images has been added that allows the renderer to create an image that profiles how long it takes to shade each micropolygon as it renders:

Display "+costfilename.tif" "tiff" "__CPUtime"

A new tiff utility program called tiffnorm can then be used to convert the data in the cost file, which stores the amount of time it took to shade each micropolygon in seconds, to an easily displayed and modifiable 8-bit tiff image. tiffnorm -q input.tif will dump the size and mix/max values of the cost image to stderr. tiffnorm -m input.tif output.tif will output a psuedo-color image scaled to the min/max values in the cost image. The user can also scale the image manually with the -l [minval] and -h [maxval]. tiffnorm -help will give a brief list of command options.

Cross Platform Shading Language Preprocessor

An RSL preprocessor is now part of our distribution and can be relied upon as a uniform preprocessor across platforms for shaders compiled with shader. $(RMANTREE)/etc/slpp is ANSI-C compliant and supports C++ style comments.  We encourage pre-processor standardization for RSL programs but if your shaders don't compile with this release, simply remove slpp from your distribution and the old behavior will be restored. The shader compiler also now defines the following preprocessor constants: __PIXAR__, __PRMAN__, and __PRMAN_RELEASE__=XXYY, where XX is the major and YY is the minor release number (i.e. 1100). It also now accepts the "-E" flag which prints post-preprocessed shader code.

Non-Raster Oriented Dicing

Non-raster oriented dicing, introduced in PRMan 10.0 for NURBs, has also been implemented in PRMan 11.0 for subdivision surfaces, bicubic patches, and bilinear patches.

Hider Motion Sampling

A new Hider "samplemotion" parameter has been added which allows the sampling of motion blurred micropolygons to be disabled. This allows for faster rendering of heavily motion blurred pictures, while still allowing the dPdtime variable to be computed as a separate arbitrary output variable pass (for use in postprocess motion blurring).

Miscellaneous Changes

• The renderer can now create a statistics report on all files accessed over the lifespan of the render using the new Option "statistics" "filelog".
• Rendered TIFF images now store the camera matrices; these matrices will be kept around if the TIFF image is converted to a texture, and may then be queried with the textureinfo() shadeop.

Bug Fixes

• RiPoints now motion blur correctly in z-depth.
• In rare cases large linear curves could split infinitely. This is no longer the case.
• Conditional RIB parsing using IfBegin now correctly handles fully-qualified Option names such as "$Option:user:renderPassType"

Limitations

• CSG is not supported for raytracing.
• Area light sources as defined by the RiAreaLightsource call have not been implemented. However, many types of area lights can be still be effectively represented in the shading language.
• Shaders are currently not evaluated during photon tracing. Workaround: use the implemented built-in photon shading models.

PRMan 11.3 Changes

• User-attribute scoping has been fixed so that attributes defined in inner scopes are now correctly popped and inaccessible to subsequent queries in the outer scope.
• User-attribute state is now correctly checked when determining whether grids can be combined for shading.
• A bug involving the recycling of file descriptors for deep shadow maps has been fixed.
• Ray-traced shadows would sometimes leave small "unshadowed" grid regions if the surface geometry of an intervening blocker object was displaced. This has been fixed.
• The rayinfo() shade-op would sometimes report incorrect depth and type information to shaders running on displaced surfaces when those shaders were running in response to a ray hit. This has been fixed.
• irradiancecache() parameters maxdist, maxerror, and maxpixeldist can now be uniform.
• More accurate filter sizes are now computed when shading ray traced geometry.
• Bugs in raytraced displaced bilinear patches and polygons have been addressed.
• The parametric space for raytraced displaced patches and NuPatches is now correct even when the original parametric range was not the unit square. Also fixed incorrect shadows cast by the same.
• A bug involving degenerate NuPatches when computing occlusion has been fixed.
• Normals at ray hit points now consistently point in the correct direction (previously they were sometimes directly opposite).
• The geometry cache used for raytracing has been significantly improved.
• A bug related to the ordering of facevarying data on a single-faced polygon mesh has been addressed.
• A severe memory leak related to polygon meshes has been addressed.
• A problem which caused some ray-tracing hit tests to over-refine the intersected surface leading to apparently stalled renderings has been addressed.
• Fetching vertex variables from primitives using the "primitive:varname" syntax when using gather now works correctly.
• TIFF textures created from 16 bit source data now have correct data in successive levels of the mipmap pyramid.
• The renderer now allows extrapolation of occlusion/irradiance values within a distance corresponding to 1/2 pixel projected into the 3D scene. This speeds up occlusion on small geometry.
• The point, normal, samples, and maxdist parameters to occlusion(), indirectdiffuse(), and irradiancecache() are now allowed to be uniform.
• The fresnel() shading operator no longer issues a warning if the angle between I and N is < 90 degrees.

PRMan 11.1 Changes

• Numerous performance optimizations and quality improvements have been added for hemisphere sampling, irradiance, and occlusion (primarily affecting the irradiance, indirectdiffuse, and occlusion shadeops).
• Raytracing bias is now applied correctly during photon tracing. Note that as a result the contributions of photons toward caustics and color bleeding may be significantly stronger between 11.0 and 11.1 since generally more photons will be deposited in the photon map. Also an issue with photon maps containing more than a million points has been addressed.
• A bug where trim curves were incorrectly applied during raytracing has been fixed.
• Two facevarying bugs (one related to a single-faced polygon mesh, the other related to motion blur segments not matching shutter times) have been addressed.
• A bug leading to overly aggressive antialiasing during raytraced displacements has been addressed. Also, raytraced displaced BLPs now maintain correct parametric space.
• A bug in multibounce, multisample gather() calls leading to a crash on Irix has been fixed.
• RunProgram RiProcedurals can now be specified relative to the procedural searchpath.
• (Linux, IRIX) SIGHUP will now correctly interrupt the render only for the purposes of printing statistics as advertised.
• (Linux, IRIX) Signal handling has been made more robust especially when interacting with child processes. This addresses problems seen with nested RunProgram procedurals. Interprocess I/O in this case has also been improved.
• (NT) In conjunction with an updated alfserver, PRMan will now reliably clean up its micropolygon cache files when a render job is interrupted by Alfred.
• The attribute() shadeop now supports a new query: "LODFraction". Returns a single float between 0 and 1 which describes the chance that the currently shaded geometry will contribute to the final color of the pixel based on the current DetailRange and Detail settings.
• The gaussian filter for the shadow() shadeop now works correctly again.
• Option "trace" "maxdepth" is no longer arbitrarily restricted to a maximum depth of 10. Setting this number higher will allow raytracing to proceed to any depth.
• Shader compiler type checking on gather() arguments has been improved.
• A problem in which gridpattern() sometimes left speckles in "oblong" grids has been addressed.
• (IRIX) Crashes during the generation of deep shadow map with color information have been fixed.
• An interaction between arbitrary output variable images and raytracing (leading to artifacts in the former) has been addressed.
• (Linux, IRIX) Dirmapping is now correctly applied to c:/path style paths, even on UNIX platforms.

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