You can add a RenderMan RIS ROP from the RenderMan Shelf or from the out pane.
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See https://www.sidefx.com/docs/houdini15.5/nodes/out/ris for RenderMan RIS ROP parameter description. For more on RenderMan options, see Rendering for more on sampling, filters, etc. |
Using RenderMan Shelf
We can use the ROP tool 
in the RenderMan Shelf to create a ROP that automatically adds an intergrator integrator VOP to your RIS Network.
Using out pane
Add RenderMAN RIS ROP
...
Add Integrator
In your RIS Network, add an integrator VOP inside your RIS Network, e.g.PxrPathTracer
...