Thursday, July 2, 2009

Basic Gamma Corrected Workflow with mental ray for Maya

by means of the Gamma render setting and Gamma Correct utility node

Now that we've got the basics down with the Maya Software Renderer, let's try to do the same with mental ray. The workflow presented here is a close analog to what we did before, but it isn't really a production ready approach. Consider it a few informative first steps.

As before, the idea is to render linear images (which would appear dark on screen) and gamma correct them for display purposes (so that they do not appear dark on screen), as this will encourage more physically correct lighting (and thus more photorealistic images). We can achieve this by setting the Gamma parameter in the mental ray Render Settings appropriately. It is found under Quality > Framebuffer. The crew over at mental images had a different idea than our friends at Alias|Wavefront when they implemented this, and they would prefer we give the actual exponent for the gamma function, rather than the reciprocal "gamma correction" value. This means we type 0.4545 (in mental ray) instead of 2.2 (as in the Maya Software Renderer), to make all rendered images brighter and suitable for display on a monitor.

Now that this is set, we can start lighting a suitable scene. Remember to NOT start lighting without gamma correction, as you will most likely have to relight from scratch once you turn it on. Just make it a habit to always enable some kind of gamma correction before ever hitting the render button (we will soon learn better alternatives to the Render Settings Gamma parameter). Likewise, you'll probably want to give all your lights a quadratic Decay Rate, at least as a starting point.