Patrick Traile

Siavash Tehrani
From my understanding of it, there are a couple of ways that applications and renderers can support MaterialX: .mtlx documents and/or through USD.

From the Houdini docs: "Solaris and Karma utilze MaterialX through UsdMaterialX". Unless you go through the process of exporting and hand-editing .mtlx documents out of VOPs, MaterialX out of Houdini ends up as UsdShade networks. I think in order for other apps/renderers to faithfully recreate complex MaterialX mats from Houdini they would need to have solid USDMaterialX support. I can't speak to Omniverse or Unreal, but from my testing there are a lot of things that don't work right in the latest versions of Renderman and V-Ray. Maybe Arnold does a better job?

At the moment I get the impression that when you hear this or that application has MaterialX support, it's really more in the limited context of textures feeding into Standard Surface. Most of the .mtlx files floating around out there seem to fit that mold.

As far as out-of-spec nodes, Karma subnets have some goodies that will only work for Karma, whereas MaterialX subnets should only allow you to tab in nodes that are part of the spec I believe.


Happy to be corrected if any of that is wonky.

Thanks Siavash, I'll see if I can get info from Nvidia and Epic side about future plans with regard to full materialX support. Having seamless interoperability across these apps with usd is awesome, but throwing in full materialX spec support across the board would just make it a breeze.

Hello, so I've been setting some cool materials using MaterialX inside Houdini, using different patterns, noises, composition nodes etc. They work great for Karma of course (both CPU and XPU) however, bring them in omniverse or unreal (which both claim to have materialX conversion for imported assets) will only acknowledge changes to the base mtlxstandard material. Not even mtlximage doesn't seem to be recognized in those applications.

My questions:

1. are those applications just lacking in proper materialX support? (which I really hope is the case lol)
2. Are any of MaterialX nodes using things outside the materialX specifications such that they will only work in houdini?
3. Are there any open source applications out there that supports USD and the full materialX spec where I can test my assets?

Jacquesf
I'm unsure of what you're trying to accomplish using the invoke graph here, but what I can tell is that there simply no 'rig' to execute in your scene animate, you pack a box using the packfolder node and call it base.rig, but it still just an inert cube, there no graph to be executed by the scene animate.

when you use invoke sop, the graph you're inputing in the first input is what gonna be executed at this very moment, what the invoke will output in your case is nothing more than the geometry you packed. the graph itself you used in the invoke do not carry over to the next step.

Thanks @Jacquesf, is there a way to have the invoke send out a rig graph?