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• Smooth normals on displaced coarse polygon meshes — This is implemented in the RixBump() utility function which is called by the PxrBump shader. This is basically just a new application of the classic trick of adjusting the post-displacement normal by the difference between the pre-displacement smooth interpolated vertex normal and the pre-displacement non-smooth (analytical) mesh face normal. 
• Volume Extinction Distance — A new control for PxrVolume allows you to choose when a volume becomes opaque in scene units. This is very helpful in creating a homogeneous fog or mist for an entire scene. Below the lights become visible as the distance is increased.

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• New emissive features for PxrVolume and PxrMeshlight together — In order to support advanced workflows where light filters or light linking are required, we now allow the PxrMeshLight light shader to be attached directly to a RiVolume for emissive effects. Next event estimation will apply for fast direct lighting. We still require a volumetric Bxdf (typically PxrVolume) to be attached. In this situation, the diffuseColor and the density parameters of PxrVolume replace the textureColor of the PxrMeshLight. All other PxrMeshLight parameters will be valid. Please see current limitations below

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