What is ambient occlusion?
I've heard about ambient occlusion and it looks nice, but what exactly is it?
Just want to add information about Ambient occlusion (AO) made by VR game developers: Ambient Occlusion: An Extensive Guide on Its Algorithms and Use in VR
Ambient occlusion is a method to approximate how bright light should be shining on any specific part of a surface, based on the light and it's environment. This is used to add realism.
Wikipedia has a nice paragraph that explains what is done.
Ambient occlusion is most often calculated by casting rays in every direction from the surface. Rays which reach the background or “sky” increase the brightness of the surface, whereas a ray which hits any other object contributes no illumination. As a result, points surrounded by a large amount of geometry are rendered dark, whereas points with little geometry on the visible hemisphere appear light.