Screen Space Ambient Occlusion (SSAO) is used for efficiently approximating the ambient occlusion effect in real-time. Compared to Global Illumination, Ambient Occlusion is less accurate as it only operates in screen space, but it has its advantages. Similar to other post-processing effects like SSR or DOF, it is important that geometries are writing to the Z-Buffer. Otherwise, they won't be affected by this technique. For each pixel, the Screen Space Ambient Occlusion samples the depth values around this pixel and tries to compute the amount of occlusion on this point.

If your graphic only contains static elements, we recommend to use the Ambient Occlusion option within the Global Illumination features. The quality is much better and more accurate. For any dynamic content, you should use the Screen Space Ambient Occlusion feature.