Holdouts are used to collect the CG objects' shadow and reflection that match very closely to the shadow and reflection in the live action plate. You can create a holdout (even without all the RenderMan parameters applied) by choosing the Holdout shelf button with your desired holdout objects selected and your ROP node. We will add the appropriate RenderMan Holdout Attribute and Attribute and set it to "on" as well as setup the correct displays and filters to generate a shadow result for compositing.

To make an object as a holdout, simply check Holdout in the geometry's RenderMan | Trace Tab or use the Shelf Button.

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