Welcome to RenderMan 21.5!

This release introduces the following improvements, fixes, and miscellaneous changes.

New Features

• Path traced (exponential and non-exponential) subsurface scattering has been introduced into PxrSurface as an option. This technique uses the same controls while providing an accurate result with a single set of controls instead of combining other techniques with Single Scatter.

• It is now possible to run the Denoise tool on EXRs exported after a compositing process if the channel names and data are preserved.

• Added color remapping features to PxrHairColor as a new Artistic mode. We default to the previous Physical mode for backward compatibility.

Scene courtesy of Krystal Sae Eua for The Mill

Miscellaneous Changes

• Substantial improvements made to Denoiser performance on the CPU, speed improvements of 2x to 4x are possible.
• Default settings for PxrMarschnerHair have changed.
• Improved sampling results when using mesh lights.
• Improved default Shadow LPE with improved accuracy and now works with light filters. Previous behavior is preserved by using the 'shadows214;' LPE prefix, i.e. lpe:shadows214;CDL
• PxrSurface now has more accurate behavior when thin shadows are enabled on glass-like surfaces; the improved behavior more accurately models the energy loss due to multiple reflection/refraction bounces. This change may cause some darkening of shadows compared to earlier versions.
• The GGX specular option for PxrSurface should see reduced noise as well as a slight change at grazing angles on anisotropic materials.
• Dramatic improvement in PxrMarschnerHair rendering speed, this might result in a slight brightness change when specularcompensation was active.
• Updated the light selection algorithm. We expect, especially in situations with very many lights, that the new algorithm will demonstrate faster iterations times and/or improved convergence per iteration.
• Max continuation length is now at least 256. Unless you have a significant number of overlapping volumes, you should not need to worry about this parameter.
• Displace shaders now receive Synchronize messages.
• Minor improvement to OSL texture access.
• Multiscatter now supports multiple samples, just like single scattering does. Also, equiangularWeight is only controlling single scatter now. Multi-scatter ignores this.
• We've added velocityMultiplier to PxrVolume, it could be helpful when converting velocity per frame to per second, etc.

• The max resident memory for PxrVCM has been reduced by around 30%.

• The time to first pixel for scenes with volumes undergoing deformation motion blur has been greatly reduced, especially when the motion blur is large and many threads are used.

• Fixed a bug where Denoise would not take advantage of all possible hardware capability on Linux machines in either CPU or GPU mode.

Bug Fixes

• Fixed a bug in AccumOpacity with Volumes.
• Fixes in the fresnel computation on PxrMarschnerHair provide stricter energy conservation across lobes.
• Fixed an issue where energy compensation was not applied correctly to non-Clearcoat lobes in PxrSurface.

• Fixed a crash when using -recover 1 with very large display resolution and/or many displays.

• Fixed bug causing incorrect matches in LPE results on aggregate volumes.

• Ray differentials computed for objects in or behind volumes are now correctly computed, eliminating discontinuities in texture filtering and improving the performance of same.

• Support width attribute for points in AlembicProcPrim.

• Fixed occasional indexing error in surface normals for SpSSDiffusion (ie. PxrSkin and PxrSubsurface bxdfs) when some albedos are black.

• Display "int matte" has been fixed to once again work as expected. Integrator developers should call RixDisplayServices::FlagAsMatte() on samples coming from matte objects to indicate to the renderer when to ignore splatted values. Plugin developers using RixDisplayServices will need to recompile their plugins.

• A bug that caused the shadow collector LPE to vary in intensity with a different number of fixedSamples to a light has been addressed.

• Fixed a random number biasing bug in hair widening. This will change noise patterns on widened hair due to better sampling.

• Fixed memory allocation bug in deep EXR output drive that would cause a crash when writing out deep data using crop windows.

• Fixed inaccurate tangents and normals computed along a semi-sharp subdivision surface crease edge which could occur at very coarse shading rates.

• Fixed possible moire patterns with the PxrRectLight

Known Limitations

RenderMan Pro Server

• Full LPE support is only available with the PxrPathTracer and PxrVCM integrators.
• Light Filters in the PxrVCM integrator do not affect or shape photon emission.
• The Cone Angle parameter for lights is incorrect, it does not match the input angle, this will be fixed in a future version.
• The PxrAovLight does not work properly with PxrUPBP.
• Analytical lights placed inside volumes may yield artifacts when made visible to the camera. As a workaround, the light camera visibility should be turned off, and a geometry with a similar shape should be used (visible to the camera, invisible to transmission and indirect rays), with the proper emissive bxdf.
• Using the '.' character in the handle for an OSL shader could cause unpredictable results during re-rendering.
• Instances are not supported for baking.
• 3d baking: no direct bake-to-ptex support.
• PxrBakePointCloud cannot directly render ptex.
• No RixPTC/pointcloud API (so PxrBakePointCloud cannot read ptc files).
• 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.
• Camera visibility changes are not respected during Live Rendering.
• For PxrUPBP, If the light source is inside a volume, that volume needs to be defined as Volume “box”
• For PxrUPBP, To get a volume caustic, the object casting the caustic needs to have higher intersectpriority than the volume.
• For PxrUPBP, Overlapping heterogeneous volumes are not working yet. (However, overlapping homogeneous volumes do work.) This will be resolved in the future.
• PxrPortalLight may yield artifacts when generating photons for PxrVCM / PxrUPBP. This will be fixed in a future release.
• 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 have mesh lights attached to them.
• Deformation motion blurred volumes don't currently work with densityFloatPrimVar or densityColorPrimVar. You will need to use a PxrPrimVar node connected to densityFloat and densityColor instead.