Tip of the Week: Speedy AO

An Ambient Occlusion Pass can be one of the most efficient ways to improve the quality of your 3D renders.

The mib_amb_occlusion node is a fast and efficient way of creating an ambient occlusion pass. If you use the ambient occlusion render layer preset, Maya will create the node by default and attach it to the Out Color of a surface shader.

If you have a complex scene with a lot of geometry, the renders can be slow with the default settings. They don't have to be. By lowering the max distance attribute, you can make significant savings in render time without much of a compromise in quality. The default value is 0, which indicates that there is no max distance - mental ray will take the entire scene into account for each point that it renders. The max distance tells the renderer to only consider influence within a given distance from each point, thereby saving render time:

As you can see, lowering the max distance speeds up the render. It also makes the ambient occlusion appear tighter; there's a faster falloff. I usually find that this actually looks better in composite. (Unless you take it too far). Tweak the settings until you have a render that looks good and a render time that you can afford. Of the four images here, I'll probably stick with the max distance of 2.5.