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

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• VFX Reference Platform 2019.  RenderMan 24 supports the VFX Reference Platform 2019.  If you haven't already upgraded your systems with the requirements for the VFX Reference Platform 2019, you will need to do so in order to run RenderMan 24.
  
  
• OSL 1.10: We have upgraded our OSL to version 1.10.  Note that in some instances, the look will be affected if you have written your own OSL patterns as some OSL noise functions have changed.
  
  
• OSL shaders now support connecting scalar values to individual elements of an array shader parameter in the same way C++ shaders do
  
  
• Allow explicitly setting dynamic array parameters in OSL shaders
  
  
• To take advantage of the new Color Management and Bump to Roughness features, you will need to expand your txmake workflows when converting your textures for RenderMan
  
  
• _MAPID_ and atlasStyle will become deprecated in future releases. Please use <UDIM>, <u><v> and <U><V> for all texture atlas specifications
  
  
• The PxrPrimvar built-in names "curvature_u" and "curvature_v" for principal curvatures are now "curvatureU" and "curvatureV" to better follow naming conventions.
  
  
• Dynamic String Construction within any in-house patterns: XPU does not support dynamic string construction within Patterns, so if your Studio has any in-house Patterns that do this, you will need to pre-compute any strings you need.
  
  
• Dynamically Building Filenames for Textures: While XPU does not support dynamic string construction, we are adding the capability to specify primvar references within a filename to have the system dynamically reference a filename for you.  This feature will be in beta2 beta for XPU, but is available in RIS now.  Use the <primstr:varname> token for this.
  
  
• The contrast-v22 and variance-v22 adaptive sampling metrics continue to be deprecated.  They will be removed in a future RenderMan release.
  
  
• In PxrUnified, volume render Oi returns single float value to an AOV when a color is expected.  The transparencyAccum of PbsWavePayload is now a color. This allows PxrUnified to correctly output a colored Oi when given volume with colored extinction. Previously, the monochromatic transparencyAccum was promoted to colored Oi and this is wrong. It is impossible to correctly composite such volumes with only the alpha channel a correct colored Oi is required.
  
  
• RfK: The "prmanPattern" terminal type has been removed from material nodes.
  
  
• RfK: The widget is now automatically set to "null" for all OSL outputs, so there is no longer a requirement that shader writers add this to their output parameters' metadata
  
  
• RfK: Alembic_In_Prman has been removed as the multithreaded advantage it had has been supplanted by the new multithreading features in Alembic_In from Foundry
  
  
• RfH: All RenderMan node versions have changed to ::2.0. please convert your nodes with provided script.
  
  
• RfH: RenderMan errors are now warnings in Houdini
  
  
• RfH: Automatic conversion of PxrHSL, PxrVary, PxrSurface, PxrMix from old scenes to the new parameter names in RenderMan 24 rely on the 456.py script on houdini scene load rather than Houdini's opalias. This is to allow us to change parameter names and keep the old values. If you already have a 456 in your pipeline, you will need to add the update methods in order to convert those shaders.

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• PxrSurface
  • Now supports two lobed Henyey-Greenstein for single scattering. Existing scenes will need to migrate the "g" parameter to the "g0" parameter.
  • The new per-instance Attribute "grouping" "int id" [0-15] can now be used to greatly reduce or entirely eliminate biasing artifacts when using the subsurfaceResolveSelfIntersections flag on PxrSurface in conjunction with path traced subsurface. Objects that wish to participate should simply be tagged with a mutually unique set of grouping ids. Upon doing so, a new self-intersection avoidance scheme should help to eliminate biasing issues that lead to highly incorrect subsurface illumination results near close intersections between the geometry, and as a consequence the need to tune or set the trace bias attributes should be greatly reduced.
  • Avoid excessive opacity calls when a utility pattern is connected to PxrSurface where we've seen a more than 2x speedup in our production scenes when large numbers of assets were wired in this way.
    
    
• A new PxrRadialDensity pattern defines a spherical density gradient in a volume container.
  
  
• Color management support.  Added basic ACEScg support. There is now a scene-wide control defining the primary colorspace (Rec709 or ACEScg). Lights, light filters and nodes with color space controls (PxrBlackBody, PxrHairColor, PxrTexture, etc) will obey this setting when set to "Scene". Patterns can override the source and destination colorspace if need be.
  
  
• You can now output AOV's in OSL via the closure debug("AOVName").  No other closures are supported, but arbitrary combinations of debug() are supported to provide AOV's.  Passing them via get/setmessage() is not supported.
  
  
• Bump and normal map shadow terminators.  There is a new parameter added to all the BxDFs to apply a technique that improves the the abrupt shadow terminator line that appear when strong bump or normal maps are used to emulate micro-geometry.  If there is no bump map applied to the BxDF the result produced is exactly the same as it was before.  By default the technique is turned off. To turn on the technique the user just needs to check the "Bump Shadow Terminator" parameter from the BxDF. This parameter is a global parameter, so its  effect will be the same for all the lobes, it means, if it is turned on then it will applied to all the existent lobes of the BxDF (1 in the case of Diffuse but many in the case of Surface).  In beta2, we are likely to make the default to be on and remove the per-material control, and instead add a backwards-compabibility option that would globally affect the render.  This is available in both RIS and XPU.
  
  
• Polgyon shadow terminators.  We have improved shadowing artifacts on coarse polygon meshes.
  
  
• RfH: improved user friendliness of cryptomatte in RfH
  
  
• RfH: apply materials to instance points via instancer
  
  
• it: Added a simple bloom filter to It
  
  
• it: Support OCIO color spaces

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