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Network Boxes not supported in USD and Edit Material Network April 11, 2024, 12:53 p.m.

Eventually yes, Houdini will utilize the UsdUIBackdrop but there are higher priorities at the moment. Houdini will need to do it for Karma and MaterialX builders. The 3rd party renderers will need to author them in their custom shader translators. And Houdini's Edit Material Network will need to recognize them for all renderers.

Mtlx Hda questions April 10, 2024, 11:30 a.m.

Thanks Rafal! truly appreciate the effort creating those files. I managed to do some tests.
You're welcome. Happy to hear it worked.

*One thing that was a bit weird is that I was able to make an .hda file without issues even though i'm on Indie. Is this something temporary or did that limitation change?
I think that's all fine. You can create HDAs in Indie, but they are saved in an indie format, so will downgrade the session if loaded into a fully commercial session.

Is this roundtrip with mtlx / hda / json still reliable for future hou versions and mtlx standards?
Yes, it's reliable, and will continue to be. That's pretty much how MaterialX standard nodes are processed for Houdini releases.

Mtlx Hda questions April 8, 2024, 6:12 p.m.

Actually HoudiniGL seems to recognize the karmaNodeGraphs.json file, so it renders the new custom shader as long as it's implemented entirely with standard MaterialX nodes.

The rough steps are:
1) Build a subnet VOP containing the implementation of your custom shader. There are some annoyances with defining subnet inputs and naming them. Pretty much the input name is imposed by the Subnet VOP, and will need to be hand-edited in step 3.
2) RMB > Save > MaterialX... to a foo.mtlx file
3) Hand edit the foo.mtlx file to add the nodedef element for you shader. Also delete the shader nodes that are outside of the nodegraph but were saved nonetheless in step 1. Remember to remove references to them from the nodegraph's inputs and outputs.
4) run the `mtlx2hda.py` and the `mtlx2karma.py` scripts on the command line to create an .hda file for Houdini (to crate new VOP nodes) and .json for Karma to render them.
5) test out by restarting Houdini, loading .hda and creating a new node.

Here is an example .hip file with steps described in the sticky notes. This file works in my setup. The .hda and .json files should be put in Houdini search path, but they also work if you just start Houdini from the command line in the foo subdir.