This scene demonstrates rendering of a volume in a complicated lighting scenario; the setup requires good importance sampling to reduce variance. The neon sign - a Geometric Area Light source (emissive geometry) - is the only light source in the scene. The volume encloses all geometry in the scene, including the light and the camera.
This example demonstrates the ability of the PxrVCM integrator to resolve complex light paths, in particular specular-diffuse-specular paths which arise from reflections or refractions of caustics. Note the caustics cast by the metal skull on the right onto the floor, and the complex refractions of caustics through the glass skull on the left. A slight depth of field effect has been added to the scene. The skull geometry was created by Morten F. Jaeger.