Ambient occlusion is a fast technique for producing soft, diffuse lighting in open spaces by using ray tracing. It is computed by determining how much of the hemisphere above a point is blocked by other surfaces in the scene, and producing a darker lighting value when the point is heavily occluded. This technique can be useful when you need a GI-like effect without paying the price for full global illumination.
With this particular example, an Ambient Occlusion light and some geometry is provided in the form of a Digital Asset. An Environment Light was used, and it’s parameters were promoted for easy access.
Decreasing the sample count allows you to improve render time at the expense of some additional noise in the render. The following render uses the same shader as the image above but decreases the samples from the default of 256 to 16. This value is set on the Sampling Quality under the Render Options tab of the Light.
If you have a smooth environment map, it is possible to replace the global background color (white) with the value from an environment map. You can also enable the Sky Environment Map under the Sky Environment Map tab.