Because it is sometimes useful for an artist to be able to experiment with a procedural materials and patterns, rather than relying on painting textures or built-in nodes, PRMan includes this SeExpr node. Based on Disney Animations's open source SeExpr system, this node is a scriptable pattern generator and combiner. It is unique among the factory plugins in its "dynamic binding" capabilities. Pattern network authors can wire upstream nodes into arbitrary (named) connection points and these can be referred to in the SeExpr script.
See the Quick Reference for more details.
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