mental ray Architectural and Design Visualization Shader Library

80 3 Sun and SkySince this is now direct light it will be picked up by FG when that is turned on. Let us comparewhat FG would “see” with, and without the portal lights:Without portal lightsWith portal lightsThe left is the super-high contrast result FG would “see” without portals, but the right is afairly well balanced scene. And not only is it already filled with subtle direct light - the skyitself is actually invisible to FG, so it never has to carry the burden of hitting a high contrastarea 8 and the problem with the final gather filter pretty much disappears.The second feature of the portal lights being direct is that if we turn FG back on, we now getonce bounce of light “for free”:One free bounce of sky lighting, courtesy of the portal lightsNotice how the wall inside the window now has some bounce light on it from the sky light,even though we are using FG with a single bounce!8 Although FG rays that directly hit the pool of light on the floor caused by the sun will indeed see a highcontrast.