Bump Roughness was created for efficiently sampling micro details in Cars 3. With this pattern, RenderMan automatically switches from a bump map to a roughness value depending on the size of a feature in the camera, effectively improving your render times by lowering the sampling rates needed to render such details.
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© Disney/ Pixar
A crucial feature of Bump Roughness is to keep micro details when objects are far from the camera, as shown in the example above.
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