Screen Space Ambient Occlusion

Ambient occlusion is a lighting model that approximates the amount of light reaching a point on a diffuse surface based on its directly visible occluders. It is commonly used to add a global illumination look to rendered images. This ambient occlusion algorithm operates on the depth buffer of the scene being rendered and associated per-pixel normals. For multiple directions defined in image space around the current pixel, the algorithm samples the depth buffer, computes a horizon angle for each sample, and integrates the ambient occlusion for the current direction based on the tangent plane, the horizon angle and a weighting function. This whitepaper includes a brief introduction to the algorithm and its parameters. For more details, please refer to [Bavoil and Sainz 08a] and [Bavoil and Sainz 08b].