...

• 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 ExtinctionExtinction 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.

...