Glossary - Occlusion

Occlusion, also known as ambient occlusion, is a shading method utilized to estimate how disclosed every point is in a display to ambient lighting. For instance, the internal part of a tube is usually more occluded, consequently darker than external parts. The deeper you go in the tube, the darker it gets. Ambient occlusion is a rate of accessibility which is computed for every exterior point. The calculation of occlusion is based on the condition. Under the open sky, it is implemented by calculating the amount of clear sky for every point. 

In the indoor atmosphere, it is done by taking the objects within a specific radius into consideration. Here, the source of the ambient light is the walls. Different from local techniques, ambient occlusion is a global one, which means the illumination at all points is a function of geometry in the display. Illumination means a group of algorithms used in computer graphics to better the lighting of 3D scenes. So, occlusion is a quite natural estimation for global illumination.

Horizon-based Ambient Occlusion

One of the most wide-spread types of ambient occlusion is Horizon-based ambient occlusion. By this technique, it is possible to approximate the real occlusion with the help of pixel depth in game development. It allows refusing the display geometry to shape an ambient occlusion map. This technique is about the shading of accessibility. It identifies the appearance depending on the easiness level of the surface that is touched by some components. The horizon-based ambient occlusion is quite famous in production animation because of its directness and efficiency. This method proposes a better understanding of the 3D shape of the shown elements. 

Screen Space Ambient Occlusion

Another very common type of ambient occlusion is Screen Space ambient occlusion. Here, the algorithm is fulfilled as a pixel shader. It analyzes the display depth buffer that is in texture. For each pixel on display, the depth rates are sampled by pixel shader around the present pixel and attempt to calculate the quantity of occlusion from every sampled point. In the most basic implementation, the occlusion factor is dependent on the difference in depth between the present point and sampled point.