I have a ‘tube’ sop with a ‘cap’ sop attached using the ‘end cap shared’ as U cap.

When i render with mantra the geo is rendered as expected. When i run a prman render with an ri_plastic shader attached the end caps are not rendered but the tube is.

Has anyone seen this behaviour before. thanks

When you use the “End cap faceted” or “End cap shared” option in the Cap SOP, Houdini actually puts a closed curve (not a surface) at the end of the tube. Houdini (and Mantra) interpret closed curves as being “filled”.
You can check this by displaying a CircleSOP in shaded mode. It looks like a filled disk. You can also check by middle-clicking on the cap operator, and you'll see what geometry you have at that point in the network.

Probably RenderMan does not consider these curves as being “filled”, so you need to use a ConvertSOP and convert the curves (“From Type” set to “NURBS curve”) to NURBS surfaces or Trimmed NURBS Surface.

Dragos

great, thanks!