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• The roughness parameter in LamaHairChiang has been reparameterized to produce a more linear response.
• The default longitudinal roughness values in LamaHairChiang have changed from 0.2 0.3 0.3 to 0.13 0.27 0.27.  (The azimuthal roughness is unchanged at 0.35).
• Some parameters in the set of the MaterialX Lama nodes have changed their name. Specifically, the "color" and "normal" names have been renamed to avoid conflict with some OSL keywords.

Deprecations

We have deprecated the C++ out-of-the-box patterns in favor of an equivalent set of OSL patterns.  The new patterns have the same names and functionality as the old patterns, so no changes to your networks are necessary.  We now provide OSL patterns because they run in both XPU and RIS, whereas the C++ patterns only worked with RIS.

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• macOS/Apple Silicon: The denoiser is not supported on Apple Silicon, even with Rosetta.  RMAN-20408.

RIS and XPU

• Color Management: Although we have upgraded to the VFX Reference Platform 2021, there are still color management limitations:
  • IT does not support OCIO 2.0 configs yet.  RMAN-19921
• MaterialX: Material layering is not supported.  RMAN-20365

RIS

• Transform edits of aggregate volumes is not working properly – pieces of the volumes will get cut off or other artifacts exist.  RMAN-20453
• The albedo on Lama dielectric goes to white at grazing angles. This differs from Lama dielectric in previous versions of RenderMan, and current PxrSurface material equivalents.  RMAN-20423
• Lama Bxdfs output albedo even when objects are matted.  RMAN-20433
• Lama emits warnings about the name of parameters Some parameters in the set of the MaterialX Lama nodes have changed their name. Specifically, the "color" and "normal" names have been renamed to avoid conflict with some OSL keywords. The parameter "newParamNames" has been added to the MaterialX Lama nodes to be able to swap between the old and the new parameter names. This will allow users the ability of using lama networks created with the old param set and still properly rendered in 25. In 26, only the new parameter names will be supported and the newParamNames parameter will disappear..  These warnings can be ignored.  RMAN-20421

XPU

• Textures in the renderer are not automatically updated during an interactive render session when using the Texture Manager.  You must restart XPU to pick up the change to the texture.  RMAN-20377
• Volume aggregates render with noisier alpha than RIS.  RMAN-20100
• Volume with colored extinction isn't rendering correctly.  RMAN-20125
• There is a ray tracing difference between the CPU and GPU components of XPU.  It is most visible in diffusion subsurface scattering. RMAN-20515
• Some AOVs in XPU are rendering differently than RIS.  directDiffuse is dimmer in XPU.  indirectDiffuse is dimmer in XPU.  indirectSpecular is brighter in XPU.  subsurface is black in RIS, non-black in XPU.  RMAN-19902
• Extinction color in PxrSurface is rendering differently in XPU than RIS.  RMAN-16771
• If you change the resolution while rendering interactively to "it", "it" will crash.  RMAN-20237
• OSL backfacing() method isn't working correctly in XPU.  RMAN-20232
• The GPU portion of XPU can render artefacts with the trace:reflectexcludesubset.  RMAN-20393

RenderMan for Houdini

• When batch rendering from a RIB exported from Houdini, the searchpath may contain an invalid path that causes RenderMan to load the wrong OpenVDB shared library, causing batch renders to fail.  The workaround is to edit the "procedural" searchpath in the RIB to $RMANTREE/lib/plugins instead of the one in the RenderMan for Houdini directory.  RMAN-20297
• RfSolaris: Displacement not working when material is referenced from /mat.  RMAN-19243
• RfSolaris: Texture memory limits are not properly respected.  RMAN-20563
• RfSolaris: If you render to "it", the render may happen twice.  RMAN-19591

RenderMan for Maya

• F-Stop is divided by 10X with PxrCamera.  RMAN-20475
• Chromatic aberration is different in RIS than XPU with RfM.  RMAN-20474
• When loading 25.0 in RfM, several warnings are in the script editor about being unable to validate OCIO configuration path.  RMAN-20565

• RfM fails to export rib to a folder that has spaces in the name.  RMAN-20517

• Bezier and Constant interpolation types for ramps are not supported.  RMAN-19486
• Overriding PYTHONPATH can cause denoising to fail.  RMAN-20546
• If you are using the RenderMan Hydra Render Delegate in Maya, and are rendering when you close Maya, there will be a crash on exit.  RMAN-18308

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Known Limitations - Existing

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