Adding the Physical Sky shader and photographic exposure

…When we're using Mental Ray, we have another option for…lighting as seen in addition to daylight and also interior lights.…We've got sky portals, and what these do is really quite magical.…What sky portals allows us to do, is designate an area,…like a window, as an opening to let the sky in.…It lets in the ambient or bounce light from…the sky in through that portal, as the name suggests.…And this way, instead of direct sun beams, we have the soft…bloom of the bounced light in the sky coming in through our scene.…

It also lets us do something even more unique.…Sky portals, because they restrict where that light comes in, allow us…to have an interior-only scene where only the interior walls are modeled.…And we don't need an exterior shell to block…the light as we would with a daylight system.…To set up the sky portal we need three key components.…We need an exposure on the camera, we need…a physical sky, and we need our sky portal.…I'll start out by getting an exposure and a sky on my cameras.…I'll select camera one, the camera I'm in.…