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- They are fast to generate. Indeed, shadow maps can be generated much faster than a normal "color" image, mainly because only depth information is needed. When rendering a shadow map, one could remove all surface and light shaders, even displacement shaders can be removed if they do not affect the geometry too much. Also, filtering (using PixelFilter command) can be lowered (even to 1x1) and ShadingRate increased (up to 10 or more).
- They can be reused in more than one render. If the scene is static and only the camera moves, a generated shadow map can be used for all subsequent renders. This often happens in the lighting stage of a production pipeline.
- They can be used to generate low cost (approximate) penumbra. Specifying an appropriate value for the "Filter Size" attribute on the light shape, one can simulate penumbra effects. This attribute is located in the "Shadows > Depth Map Shadow Attributes" group. When a light has an associated RenderMan light shader, this is usually controlled by a "blur" attribute directly on that shader instead.
- They provide fairly good results when used carefully.
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