# Screen Space Ambient Occlusion (SSAO)
SSAO helps to manage the occlusion of the environment through the screen effect. Occlusion is a shadow that occurs as a result of multiple reflection of the light beam between two planes that are located at an angle of less than 180 degrees relative to each other.
SSAO works with shading at the intersection of two planes. It helps to achieve a more realistic picture.
The effect of self-shadowing can be created using Materials and the Ambient Occlusion parameter (for more information, go to the Materials). But it will not work if you need to achieve this effect on objects where materials have not been applied.
In the real world, if objects are located close to each other, one of the objects should have self-shading. If it does not happen, the objects may look artificially in the Scene. The SSAO post process is just right for solving this problem. This effect occurs on the screen space. Like all post processes, it is applied to the final picture.
Let's look at the example below. Before applying SSAO there were objects that did not affect each other at all.
After turning on SSAO, the picture became more realistic. The intersections of the objects have become darker. This is how the SSAO post process works, it adds shadings between objects (in areas where their planes intersect).
SSAO has 2 parameters: Radius and Intensity.
### Radius
Radius is measured in units and determines the occlusion radius. A large radius is useful for huge objects (for example, houses or skyscrapers).
For small objects, we set an acceptable radius. For example, 0.1.
### Intensity
Intensity affects the intensity of shading. The higher the value of this parameter, the darker the shading between objects.
When we turn on the SSAO post process, we see that a soft shadow appears in all areas where there are intersections of planes.
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