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Here, it is important to distinguish between two types of plugins: ones that need to create many short-lived lightweight instances over during the course of a render, and ones that do not. RixBxdf, RixDisplacement, and RixLight represent lightweight instances that may be created many times during the course of a single render, and therefore are not directly subclasses of RixShadingPlugin. Instead, instancees of those classes are returned by the appropriate Factory (e.g. RixBxdfFactory), with the Factory itself being the subclass of RixShadingPlugin.

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All shading plugins are expected to return a description of their input and output parameters via the GetParamTable() method. This returns a pointer to an array of RixSCParamInfo, containing one entry for each input and output parameter, as well as an extra empty entry to mark the end of the table. This parameter table is used by the renderer to ensure proper type checking and validate the connections of upstream and downstream nodes. As such, each entry in the table should set a name, a type (RixSCType enumeration), detail (varying vs uniform, RixSCDetail enumeration), and access (input vs output, RixSCAccess enumeration). These declarations also need to be kept in sync with the associated .args file.

For an example of usage, consider a pattern plugin which returns a color. The resultC output parameter is a color, so it is defined in the parameter table as:

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