The 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. MaterialThe representation of the surface or volume properties of an object. option is used in pathtracing type kernels, eg “pathtracing” and “pmc”. (not direct-lighting/ambient occlusion). Please refer to the Otoy forum “Resources and Sharing” for a tutorial on using portals.