I would like to have different shaders showing when working in the realtime viewport (GL/Vulkan) and with Karma. I tried using a collect node and connecting a usd preview surface and mtlx standard surface to it. but because the mtlx shader can be displayed with GL as well it would pick that instead of the usd preview surface. I also tried to use a configure primitives LOP to set the two shader's purposes, but that didn't work either. Is there a way to tell solaris exactly which shader to use (in the end I would even like to have two mtlx shaders).

We found using both a karmaMaterialBuilder and a usdMaterialXbuilder fed in to a collect node allows for setting up simplified preview materials in 20.5

Something along these lines:

Could try this.

"HOUDINI_GL_USE_MATERIALX

Enable support for MaterialX and Karma materials in the Houdini GL render delegate in the LOP context. The default value is 1.

0

MaterialX and Karma materials are not supported.

1

Both MaterialX and Karma materials are supported.

2

Only MaterialX is supported."

https://www.sidefx.com/docs/houdini/ref/env.html [www.sidefx.com]

Ben Toogood Aardman
We found using both a karmaMaterialBuilder and a usdMaterialXbuilder fed in to a collect node allows for setting up simplified preview materials in 20.5

Something along these lines:

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Thanks, we will do exactly that!