This is the so-called “Twilight” renderer. Included are a the “standard ray tracer”, a path tracer, photon mapping, a bidirectional path tracer, and processors for radiosity as well as metropolis light transport. The raytracers can be used for both light modelling within your RGG model as well as for rendering your scene. The following introduction covers the raytracing settings when used for rendering. To use the Twilight renderer,
All the raytracers and their concrete implementations are explained in-depth in these three reports (in German)
The raytracing settings for rendering can be customized under <key>Preferences –> Renderer –> Twilight</key>. The ray processor can be selected from the “Ray processor” drop-down menu. When changing parameter values in the preferences, you always have to leave the field you changed with your cursor before closing the preferences window (just click in a different field) for your changes to take effect. You can find an overview of the different raytracing algorithms to choose from besides their relevant settings in the algorithm section.