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• XPU - for an overview of XPU in RenderMan 24
  
• Shader & Look Development with XPU - for details on lookdev with XPU
• Features & Limitations - to understand the differences between XPU and RIS XPU Notes - and for known limitations in XPU

The Artist Experience

RenderMan version 24 provides major upgrades to Look Development, with many tools that improve artist workflows and complement the creative process. By collaborating closely with Industrial Light & Magic and Pixar Animation Studios, we bring you innovations that have been developed for some of the most ambitious VFX and animation work in the world. 

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• Shading
  
  • PxrUnified integrator is currently experimental as it does not yet support all the standard rendering features.
  • PxrSurface back diffuse color is not output to the albedo color AOV
  • <primstr:nameofvalue> substitution of data from a constant primvar or user attribute on an object for dynamic filename substitution is not yet working for the gettextureinfo() OSL call.
  • Using the ' . ' character in the handle for an OSL shader could cause unpredictable results during re-rendering.
• Performance:
  • OSL startup.  We have upgraded to OSL 1.10 for both RIS and XPU in RenderMan 24.  We have found that this upgrade (and its dependencies) have slowed down time to start up.

  • Volume integration with patterns.  Because of the switch from C++ to OSL patterns and the sensitivity of volume integration to pattern execution, there are performance regressions with volumes in RenderMan 24 compared to RenderMan 23 that remain to be addressed. This is most noticeable when the volume density is connected to a pattern (e.g. PxrPrimVar); the performance regression can be avoided by avoiding a pattern connection if possible.

• Interactive instrumentation/statistics:
  • Bridge product (Maya, Katana, Houdini, Blender) initial integrations are available, but are turned off by default.  Artists can turn on the statistics through the buttons in the UI.
  • Web browser integration is still to come and is now likely to arrive in a future version of RenderMan.
• General rendering
  • Load on demand procedurals are not supported anymore, all procedurals are now loaded immediately
  • We do not read point data from OpenVDB files
  • Per-Instance baking is not supported, only the reference instance.
  • 3d baking: no direct bake-to-ptex support.
  • PxrBakePointCloud cannot directly render ptex.
  • Sample/Display filter plug-ins do not have access to lighting services for light dependent effects, e.g. lens flare.
  • Adding new mesh light on existing geometry during IPR results in double geometry.
  • Motion blurred polygons do not motion blur normals when deformed. Use Subdivision meshes instead.
  • When attempting to access an array primvar, you must first check the size of the array primvar and allocate the appropriate space. Not doing so may lead to a crash.
  • Points and curves cannot be used as geometric lights.
  • Analytical lights placed inside volumes may yield artifacts when made visible to the camera. As a work around, the light camera visibility should be turned off, and a geometry with a similar shape should be used (visible to camera, invisible to transmission and indirect rays), with the proper emissive bxdf.
• Bridge Products:
  • RfH: Soloing Lama nodes in complex shading networks can give incorrect result

RenderMan XPU

• Constant folding in patterns: There remains an issue where we are not properly constant folding input into OSL patterns in special combinations, causing a rendering failure.
• OSL Patterns:
  • <primstr:nameofvalue> needs to be implemented as a way of specifying primvar references within dynamic filenames.
• Several minor shading differences between RIS and XPU
• Out of Memory crashing: If the GPU runs out of memory, XPU will crash.  The intent is that we will be robust to crashing in this case in a future release and will instead stop rendering and issue a warning to the artist.
• Nested instances will render, but if you are using attribute variation to vary materials within the nesting, the results will be incorrect.
• If you update a texture while the renderer is running, XPU may not update the texture.  If this happens, restart your render.
• If you stop interactive rendering while textures are still being made, sometimes you will get a crash
• RfM does not yet support batch rendering with XPU

• See the XPU section of the documentation for a further Please refer to the XPU section of the documentation for the current list of limitations.