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Like it's name states, leaf-level instancing only works on scenegraph Scene Graph locations with no children.  RenderMan for Katana will not traverse past a location with the instance.ID attribute, so it cannot be used to instance groups of geometry.  If you need to instance a hierarchy, you will need to use either hierarchical instancing or an instance array.  These are described in the next two sections.

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Just like in hierarchical instancing, this approach uses direct assignment of locations as an instance sources.  Locations marked as instance sources can be referenced by the instance array location.  This approach has some advantages and disadvantages over hierarchical instancing.  The main advantage is that you only need to create one scenegraph Scene Graph location to represent all your instances.  This can save on Katana scenegraph Scene Graph processing time.  Additionally, you can reference multiple instance sources in a single instance array.  The main disadvantage is that instance arrays do not provide ways to override materials per instance.  It is important to determine your requirements before deciding on an instancing method.

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