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Instancing can save on memory but may impact performance such as time to first pixel (how quickly a render begins sending pixels) since Katana may process many nodes. Options where you can instance a hierarchy will be more efficient for time to first pixel but you may lose control of some attributes you may wish to override, this is the trade off. In the PrmanGlobalStatements you can specify You can read more about nesting versus flattening on the main Instancing page. Essentially, the SceneGraph flattening time corresponds to the number of instances multiplied by the number of locations below the instance source. The more complex your instance sources are and the more instances you have, the greater the cost of flattening becomes. |
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While you can vary Bxdfs, transforms, light linking, and attributes per instance, there are some things that cannot be varied. PrimVars and parameters under the "primvars" and "primAttributes" groups in PrmanObjectStatements cannot vary per instance. Displacement also cannot vary across instances because it changes the representation of the geometry prototype in the renderer. For a more in-depth discussion about instancing, please read the Instancing page in RenderMan documentation. It provides some great background information as well as the full list of what can vary across instances.
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