Welcome to RenderMan 21.6!

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

New Features

• Added a control for "thickness" for Physical Clear Coats in PxrSurface.
• Added new ground selections to the PxrEnvDaylight simulation: 
  • Legacy: Old behavior
  • Clamped Hemisphere: "Smear" horizon values on the virtual ground plane
  • Diffuse Ground: A fake infinite ground plane with diffuse color

Miscellaneous Changes

• Path Traced Sub-Surface Scattering control Zero Scatter Attenuation has been replaced by an IOR parameter causing total internal reflection.
• Added intensityNearDist parameter to PxrMeshLight.

• Improved live-render edit speed in cases where several LPE based AOV's were being used.

• RenderMan will now abort when attempting to recover non-incremental renders when bucket order is set to anything other than "vertical" or "horizontal".

• In OSL, gettattribute() of the "context" object can be used to access the members of the RixShadingContext scTraits structure "eyePath", "lightPath", "primaryHit", "missContext", "reyesGrid" and "shadingMode".

• Extended widget types for OSL nodes loaded at startup: 'fileInput', 'assetIdInput', 'filename' (non-standard), 'text', 'popup' and 'boolean'.
• Fixed a crash when parsing OSL shaders with int parameters using 'min' or 'max' metadata.

• Improved quality of deep output compression when a deep id channel is present.

• Increased the upper range for RixKtoRGB, below we show new values above 10000

Bug Fixes

• Fixed bug causing potential crash when using aggregate volumes.

• Fixed bug that could cause a crash when using a gprim with very many vertices and/or primvars.

• Fixed bug causing reduced thread efficiency and potential hangs when rendering many things with different grouping membership, enabled lights, or enabled lightfilters state.

• Fixed a potential crash when a hierarchical subdivision mesh specified an invalid face index in a face edit.

• Fixed bug causing a very small chance of crashing when rendering a scene containing both infinite and local lights.

• Some fixes for subsurface scattering with the PxrVCM (and PxrUPBP) integrator(s) that may have cause them to render black or with artifacts.

• Fixed potential for crash or extra memory usage when rendering a large polygon mesh having non-quad faces and __faceindex values for per-face textures.

• Fixed tile-shaped artifacts on materials with both subsurface and diffuse transmission.

• Added the correct attribute for importanceMultiplier to the PxrMeshLight

• Fix of incorrect normals of instanced NURBS patches with non-homogeneous control points. Speedup of ray tracing of some NURBS.

• In OSL, trace() and getmessage("trace") now work when hit objects are not shaded.

• Fixed a bug that could cause incorrect interpolation of primitive variables in some cases of coarsely tessellated displaced surfaces.

• Fixed a possible issue with alpha values on matte objects and volumes.
• Fixed a bilinear interpolation bug in the EvaluateAtLimitMultiple() call of the SubdivEval API

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.