mental ray Architectural and Design Visualization Shader Library

3.8 Sky- and Environment Portals 81Using portal lights and 3 diffuse bouncesUsing GI (Photons)Turning on multiple diffuse bounces (on the left) makes the image come alive. Turning onGI (Photons) now yields a much more balanced image because the portal lights actually shootphotons! No longer is there the big skewing in favor of bounced sun light, the sky light willbounce equally well in the form of photons.Finally, turning on one of the indoor lights, and utilizing the portal lights transparencyparameter to combat the overexposure of the outdoor view, we get a final image:A final imageIn conclusion: The portal lights help...• ...reducing render time (by reducing the need for using extremely high FG settings).• ...maintain the light balance in the scene (by converting environment light to photons,which can bounce around indoors just as well as sun light).• ...increase the quality of the sky lighting, making smooth areas smooth and blotch-free,as well as revealing the most minute detail with full fidelity.• ...dramatically reduce scene set-up time (by requiring little to no tweaking, alwaysgenerating the “optimal” image out-of-the-box).