Ambient Occlusion

What is Ambient Occlusion?

Ambient occlusion (AO) is a shading and rendering technique that calculates how exposed each point in a scene is to ambient lighting. Areas where surfaces meet at corners, inside crevices, or under overhangs receive less ambient light and appear darker. This subtle darkening dramatically enhances the perception of depth and three-dimensionality in rendered images.

The technique works by casting rays from each surface point to determine how much of the surrounding hemisphere is blocked by nearby geometry. Points deep inside corners have most of their hemisphere occluded, resulting in darker shading. Points on flat, exposed surfaces have clear access to ambient light and remain bright.

In architectural visualization, ambient occlusion adds crucial visual information that helps viewers understand spatial relationships. The subtle shadows where walls meet floors, the darkening inside window reveals, and the soft gradients under furniture all contribute to making rendered spaces feel tangible and real.

Ambient occlusion is often used as a complement to direct lighting calculations rather than a replacement for full global illumination. It's computationally efficient and can be applied as a post-processing effect, making it valuable for real-time applications and quick preview renders. Many visualization workflows use AO passes that can be adjusted independently during compositing.