You can create shaders in /mat in the arnold_materialbuilder vop network as well as the old way in /shop in the arnold_vopnet vop network. Use the material flag to enable picking of the vopnet as a material at the object level.
There are three types of output depending on the purpose of the shader network; Material, Light, and Environment. The result of the shader network must be connected to the input of the relevant output node. Multiple Outputs of different types can be contained within the same shader network. If multiple outputs of the same type exist, Arnold will use the first one translated by HtoA.
- color: For attaching a shader (like a Physical Sky) to be used as the color of a light.
- light_filter #: Light Filter nodes are connected here. As each is connected another input will appear.
- atmosphere: For connecting the atmosphere nodes fog and volumetric scattering.
- background: For connecting background shaders like Sky or Physical Sky.
To assign a vopnet drag it from the SHOP onto the geometry or use the Operator Chooser in the geometry Material tab.
The 'jump to operator' in the material tab will go to the Arnold shader network, rather than jumping to the shader inside. This is Houdini's behavior because you're assigning a SHOP and thus it brings you to it, not inside.
You can export materials in an arnold_vopnet or from an OUT_material VOP by right-clicking with the context-sensitive menu. This exports all of the shader graphs connected (surface, displacement, and volume).