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The seasoned RenderMan user will notice this is all very similar to how displacement was done in the classic RenderMan Shading Language (RSL) – see for example example the "Advanced RenderMan" book by Apodaca and Gritz, 2000 section  section 8.2.  One notable difference is that the displacement calculations used to be in camera space, but in RenderMan 22 they are in object space.