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shop_displacepath on per primitive base?

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Hi there,

I'm trying to wrap my head around renderman 20 in houdini 15.5.
Now there's a tricky thing with displacements going on.

When building stuff, I usually group the entire object in a single geometry node
via subnet and combines, applying materials via the material SOP and specific groupings of the
underlying geometry. this in turn creates a string attribute on the selected primitives
with name “shop_materialpath” and the given path to the pxrWhatever shader.

stuff shows up in RIS renders, everything behaves as expected. fine.

this would behave equally, if I just added the “shop_materialpath” via AttributeCreate and
the proper path to the shader by hand on a primitive.

however, now I want to displace something.

the only working way in renderman 20 seems to be to create a pxrDisplacement with some input
(f.e. pxrWorley) and add the rendering parameters “Displacement Shader” (shop_displacepath)
and “Displacement Bound” (ri_dbound) to the geometry node in /obj.
Apply the shader, set bound > 0, displacement shows up in renders. fine.


Now I thought: “Hah. Just transfer these parameters on a primitive base via AttributeCreate as well, done.”.

However this doesn't seem to work. Instead I have to extract the geo into a second geometry node
in /obj via ObjectMerge and again apply the said parameters on the top-level geometry node itself.

Are “shop_displacepath” and “ri_dbound” not assignable to primitives by hand?
Or am I missing a crucial step? Perhaps something else has to be applied as well?

Any Ideas? smile.png


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Any suggestion on this topic? I understand the only way to assigning shaders and displacement shaders is at object level?

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