Karma and Houdini
Karma is the replacement for Mantra (which was not designed for the USD file format). It provides both CPU and XPU (GPU) options — as of Houdini 20/20.5, Karma XPU is gold and CPU is production ready. When discussing Karma, USD and Solaris should also be mentioned. A new shader paradigm called MaterialX can be used alongside it, though the principled shader is still respected in CPU (for XPU use MaterialX only). See also Redshift for an alternative renderer.
Official reference: SideFX Karma docs · Compare Karma builds · Karma FAQ
- Create a LOP network in the obj context → use Scene Import All (or SOP Import) — easiest entry point for beginners
- Use Stage / Solaris → Scene Import node (or SOP Import)
- A Karma node exists in the out context however be aware that it can be inconsistent with viewport update and is not recommended - if you dive inside, it is just a usd rop and a lopnet; Solaris is recommended
Entagma has an excellent short walkthrough: Test-Driving Karma XPU & MaterialX
- TIP: use Ctrl+T to create another tab and pin it for easy access to network, shop, out, etc.
- TIP: scene import all can be used if you like working in obj (we will explore more sophisticated/efficient techniques, but this is a quick start)
- NOTE: XPU may not work depending on your graphics card AND drivers — be sure to install NVIDIA GeForce Experience drivers (troubleshooting tip)
- NOTE: MaterialX will not work in Mantra and may not show in OpenGL; as of Houdini 20.5 the default viewport is Vulkan (beta in 20.5)
- WARNING: XPU and CPU renders will not match — BRDF interpretations differ
Originally developed at Lucasfilm; released open source in 2017 with contributions from Sony Pictures Imageworks, Pixar, Autodesk, Adobe, and SideFX. MaterialX nodes are not written in VEX/VOPs — you can't dive inside, but you can join them with VOPs. Any render delegate supporting MaterialX can use these materials — think of it as USD for shaders.
- Shading in Karma
- color variation with MtlX
- adds another MtlX option
- MtlX Geometry Color node, rounded edges
- YouTube: Karma + MaterialX overview
In Houdini 20, the material linker node directly accesses AMD materials (click the gearbox).
-
hiplc ⬇ karmaMtlxgroups.hiplcuse groups and packing to bring pieces into LOPs
-
hiplc ⬇ karmaMtlxName.hiplcuse groups and name node (or name-from-groups later in your network)
These solutions work for principled shaders as well as MaterialX.
You can also use groups in the pack version for easier identification of parts instead of "obj1" or "mesh0" etc. Also introducing wild cards for identifying and component-builder
- groups with name node for easier identification
- wildcards and component-builder