"AO" stands for Ambient Occlusion

In reality, light will scatter in any direction, and its intensity will always change, so the part of the scene indirectly illuminated should also have varying intensity, rather than the invariable ambient light. One of the indirect lighting simulation is called ambient occlusion. Its principle is to approximate simulate the indirect lighting by darkening folds, holes and very close walls. These areas are largely obscured by the surrounding geometry, so it will be difficult to lose light, so these areas will look darker.

Ao is used to describe the effect of blocking the surrounding diffuse light when the object intersects or approaches. It can comprehensively improve the details, especially the dark shadows, enhance the sense of hierarchy and realism of the space, strengthen and improve the contrast between light and shade of the picture, and enhance the artistry of the picture.

The visual impression of Ao special effect is mainly reflected in the brightness of the picture. The picture without Ao special effect is slightly brighter; After the Ao special effect is turned on, the local detail picture, especially the dark shadow, will be more obvious. It improves the shadow to achieve better visual effect, improves the depth and hierarchy of the scene, and greatly enriches the image details. These small masking details bring a stronger sense of depth to the whole scene.