Is there a way in Karma to do cameraprojection in shader (or for that matter any kind of projection)?

Yes, use a USDCoordsys to create a reference coordinate system, then in the shader use that coordsys' name in a space parameter on one of the mtlx transform nodes or on the mtlx position directly.

Thanks for the pointer. I also found an example in the docs but boy do I not understand how that works and why it needs to be setup in that way. For example why does it only work if the material is parented under the "World" primitive?

ronald_a
For example why does it only work if the material is parented under the "World" primitive?

yeah, it's kind of annoying that the hierarchy is restricted this way due to some USD reasons. The material, camera, and target need to be able to find the coordsys, and they can't find it if they don't share a common ancestor. USD is 'rootless' so without creating a true root, for example the 'world' primitive, the prims won't share a common ancestor.

jsmack
USD is 'rootless'

I believe it's spelled ruthless, at least from my experience

jsmack
The material, camera, and target need to be able to find the coordsys, and they can't find it if they don't share a common ancestor

The camera doesn't need to live in the same hierarchy. As for the rest of that, we're looking into a possible implementation issue in Karma. For *now*, yes, the coordsys binding should be applied on a parent prim common to the geometry & material.

jsmack
Yes, use a USDCoordsys to create a reference coordinate system, then in the shader use that coordsys' name in a space parameter on one of the mtlx transform nodes or on the mtlx position directly.

May I ask how to assemble this USDCoordsys in materialx shader builder?
I need to project a displacement map on geo.