Ambient Occlusion is a trick invented by film makers to get an indirect illumination effect in a controllable way. For every surface point, you sample the surrounding geometry in every direction, and estimate how much incoming light is blocked from reaching the surface point. You can either use the data directly in your shader networks, or bake it down into a map to avoid rerenders or for game content.

Ambient Occlusion is a great tool for adding subtle shading to your images. It's difficult to tune your final gather renders to be really flicker-free, so approximating a similar effect with Ambient Occlusion maps is a great way to avoid flicker.

Thanks to Kalle Löfberg for the basic form of the craft.

Download pdf.