I'm trying to get my head around how I would be able to create variants upstream. Scenario is the following
There is a asset.usd which has 3 layers (model, anim, shade). Now in a specific shot or sequence we need to add a dirt layer to the asset. Since this is done only on this sequence/shot I would like to create a shade_variation.usd layer.
The problem now is that.. well I don't know how to go about it. I need the existing shader from shade.usd and add a texture network plugged into it. I tried something similar in another thread https://www.sidefx.com/forum/topic/71116/ [www.sidefx.com] but that didn't lead anywhere.
This was suggested but I'm not sure how to actually do that with the LOPs nodes.
This can be a reference to another prim in the scene graph rather than a reference to a separate file on disk. So suppose you have /mats/material1 on which you want to create variants. Instead of creating the variants on /mats/material1, you would deactivate /mats/material1, and create /mats/material1_with_variants that is a reference to /mats/material1. Then define your variants on /mats/material1_with_variants.
StefanA I need the existing shader from shade.usd and add a texture network plugged into it
One option could be to use Edit Material LOP. It should work for simple USD shaders, though it may break for more complex networks.
The Edit Material LOP does not create a shader variation upstream, but rather can be used to tweak the material or shader downstream.
Another option may be to pursue the suggestion from the other thread, and create some material variants upstream, and then switch between them depending on the shot.
I guess there is no way around it, we need to add of the material variations and have that in the shade.usd Edit material didn't work at all with the arnold shaders, but that might be a bug. But I'm now thinking that if we add more textures or “things” in the shade.usd we should probably be able to control it with edit properties since most of these variations would be controlled by switch nodes.
Instead of using a material switch, maybe you could place the switch more on a layer position in your shader built itself trigged by a string attribute attached to your shot description. At least you could only have one main material definition to change, and not have several?
Just a thought, didn't have to look at this yet myself
vincent*
________________________________________________________________ Vincent Thomas (VFX and Art since 1998) Senior Env artist & Lighting & Creative Concept design http://fr.linkedin.com/in/vincentthomas [fr.linkedin.com] Available (febrary 2020)
