Ambient occlusion facts for kids
Ambient occlusion is a technique used in 3D computer graphics to estimate how light behaves. The physics of how photons of light can occupy a space says that inner corners of objects (or space where two objects are close to each other) have less light and appear darker (have more shadow).
Imagine being inside a matte white cube with even light; the surface color is exactly the same so theoretically you shouldn't be able to see any corners or edges; but because of the described effect you can.
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Ambient occlusion Facts for Kids. Kiddle Encyclopedia.