Unlike other RenderMan bridge products, PxrLayerSurface is not exposed in the interface because all layerable parameters must be present in order for layering material parameters to work in Houdini.

You can find out all the details of PxrSurface and its layerable parameters by visiting the Pixar Surface Materials.

PxrLayer

We can override the parameter in PxrSurface using PxrLayer. Connect the output of PxrLayer to PxrSurface's PxrLayer.

In this example, we set a green diffuse color in PxrSurface. Then we layer a PxrLayer node on top that has a cyan diffuse color.

PxrLayer Mixer

We can combine layers using PxrLayerMixer.  Connect the output of PxrLayerMixer to PxrSurface's PxrLayer.

We can layer specular, iridescence, and other illumination lobes.