Deborah R. Fowler
Houdini Karma Shading Examples
General Principles CPU vs XPU
In Karma CPU you can use both the Principled Shader and MaterialX; however, in Karma XPU, only MaterialX is fully supported.
General shading principles still apply as described on the overview of shading page. For example, you still require proper UVs for textures to map correctly to your objects.
See also Textures in Karma for more examples related to image textures and noise.
MaterialX Examples HIP Files
There are many free shaders accessible via the Material Linker that can be used from either the standard catalog or AMD catalog. The examples below focus on tweaking these materials:
Described also on the Karma and Houdini page with a corresponding Karma Quick Start video are the following files:-
hiplc karmaMtlXColorVariation.hiplc— Basic color variation
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hiplc karmaMtlXgroups.hiplc — When pieces of objects need to come into LOPs using groups and packing will help
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hiplc karmaMtlXRamp.hiplc — Additionally, implementing ramps in MaterialX
USD Format Structure Reference
To help understand the underlying structure of USD materials, I referenced some of the files that are in the install from when Karma was in 19.0.383.
Those materials have been consolidated into one usd file, however they are still accessible
in C:\Program Files\Side Effects Software\Houdini 20.5.278\houdini\materialx_resources\Materials\Examples\StandardSurface and pulled them in using a file node and assigned with assign material node
Looking at standard_surface_glass.mtlx gives a better idea of how these shaders are stored in USD format:
Editing Properties Solaris Workflow
In Solaris, you can use an Edit Material Properties node to adjust parameters on your shader.
Pro Tip: An even easier way is to use VEX inside the Assign Material node to perform overrides.
