View Ambient Occlusion
Ambient Occlusion (AO) is a shading method that is often used as a replacement to Global Illumination because it can be much faster to render and easier to control, at the expense of accuracy. Visually-speaking, ambient occlusion adds extra soft self-shadowing, very apparent in cracks and crevices, and gives the image more realism. A common technique is to render the scene in as normal and then render out a separate Ambient Occlusion pass. Then, both image passes are loaded into a compositor, and the ambient occlusion pass is multiplied onto the original image, adjusting the strength to fit the needs of the shot.