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To add a material, we need to first create a RIS Network.  Note that RIS material is not a SHOP but it is a VOP inside aan RIS Network.

  A RIS Network is just a container for RIS VOPs.  It is required for Houdini to work with RIS materials. New in RenderMan 22 - a Important: A material is represented by a PxrCollect VOP with a BxDF VOP input. To add a material, you can add a PxrSurface from the RenderMan Shelf, which automatically creates a PxrCollect, or select another BxDF from the RenderMan Menu to wire into a collect VOP. These tools also automatically create a an RIS Network if it does not exist as well as the selected VOP.

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To render, add a RenderMan 22 ROP from the RenderMan Shelf. This tool also creates a RIS Network and sets the integrator to PxrPathTracer. Make sure the Camera parameter is set to the render camera, then press the Render button to see your render interactively in the Image Tool. See Rendering for more information.