mental ray Architectural and Design Visualization Shader Library

96 4 Camera- and Exposure Effectscrush shadows = 0.2 crush shadows = 0.6The crush shadows parameter deepens the lower end of the intensity curve, and we getsome very nice contrast. However, since this image is already near the “too dark” end of thespectrum, it tends to show an effect of darkening the entire image a bit.This can be compensated by changing the exposure. Lets try a couple of different shuttervalues, and prevent overexposure by further lowering our burn highlights value:shutter = 50, burn highlights = 0.1 shutter = 30, burn highlights = 0.1The final image is pretty good. However, since so much highlight compression is going on, wehave lost a lot of color saturation by now. Lets try to finalize this by compensating:saturation = 1.0 saturation = 1.4Now we have some color back, the image is fairly well balanced. We still see something existsoutdoors. This is probably the best we can do that is still physically correct.However, remember we were using the portal lights for the window? These have a non-physical“transparency” mode. This mode is intended to solve exactly this issue. Even though theresult we have so far is “correct”, many people intuitively expect to see the outdoor scenemuch more clearly. Since our eyes does such a magnificent job at compensating for the hugedynamic range difference between the sunlit outdoors and the much darker indoors, we expectour computers to magically do the same. Using the transparency feature of the portal lights,this can be achieved visually, without actually changing the actual intensities of any lightgoing into the room: