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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 because 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
• OSL manifolds now only take combined 2D primvars (st versus s, t) for increase performance in XPU.
• 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 a dot release for XPU, but is available in RIS in R24.0.  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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