Convincing fur effects can be created with PRMan through the use of RIB generators. When a fur RIB generator is attached to an object and set up correctly, it generates numerous curve primitives on the objects which are shipped off for rendering in PRMan. These curves, RiCurve primitives, appear as hair.
There are three types of RIB generators included with the RenderMan Artist Tools which are capable of producing fur effects. The source code is provided for further customization.
mtorFuzz: When attached to an object mtorFuzz can produce something akin to "stubble". It was created as an example of a RIB generator, and is the precursor of the other mtorFur RIB generators.
mtorFur: MtorFur has a large number of parameters and can create a wide variety of fur effects. Parameters can be animated with TCL scripts.
mtorUltraFur: If you have access to Maya Fur, then you can use mtorUltraFur. MtorUltraFur is a smart RIB generator which can read Maya Fur files. Simply set up Maya Fur, render out the fur files, and mtorUltraFur can generate fur. This means all of Maya Fur's many parameters can be adjusted, texture maps can adjust parameters, and attractors are supported for dynamics and keyframe animation techniques.
MtorFur and mtorUltraFur evolved from mtorFuzz; they have the advantage of allowing much longer hairs, with controls over more aspects of their appearance. In addition, mtorUltraFur integrates with Maya Fur, allowing you to use Maya's own tools to comb and map the attributes of your hairs, or even animate their movement using Maya Attractors.
Source Code: Also available for developers who want to make further customizations is the C++ source code and .sli files, which can be found in the devkit/examples/ribgen subdirectory of your RAT installation.
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