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• The new material workflows requires that the most downstream VOP node is a PxrCollectPxrMaterialBuilder, even for lights. Please insure when loading old scenes that the shop_lightpath points to a PxrCollect PxrMaterialBuilder VOP.
• Pxr Std Lights (which are RSL lights) were deprecated in RenderMan 21. Create a new Pxr C++ light.  See Adding Light.

Shading

• RSL (RenderMan Shading Language) support has been removed. Materials are C++ constructions and patterns should be OSL when possible.
• We accept the Houdini attribute names for use in shading by connecting a PxrPrimvar or PxrAttribute node to a parameter using the appropriate name.

Geometry

• Poorly tessellated (non-subdivision) surfaces may show artifacts when rendering like dark edges and outlines. It's recommended to render smooth subdivisions to avoid this artifact. You may also use polygons with no normals defined and then subdivide, RenderMan will compute the normals for you.

Rendering

• The RenderMan RIS 21 ROP renders using the 21 soho Soho workflow. It is recommended to use a new RenderMan RIS_IPR ROP to take advantage of the interactive workflow in RenderMan 22.