A PortalA technique that assists the render kernel with exterior light sources that illuminate interiors. In interior renderings with windows, it is difficult for the path tracer to find light from the outside environment and optimally render the scene. Portals are planes that are added to the scene with the Portal material applied to them. optimizes light source rendering by helping the render kernel find important light sources in the scene. For example, interior scenes illuminated by an outside light source that comes in through windows can be difficult for the path tracer to optimize the light as it enters the interior environment. To help the path tracer find these light sources, place a surface plane outside the window, then apply a Portal material to the plane to create a portal plane. This setup improves the quality of the light and increases the render's efficiency (figure 1).
The Portal MaterialThe representation of the surface or volume properties of an object. option is used in pathtracing type kernels — e.g., “pathtracing” and “pmc” and not direct-lighting/ambient occlusion. Please refer to the Resources and Sharing Otoy user forum for a tutorial on using portals.
Figure 1: A surface plane used as a Portal light source.