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Aggregate volumes are designed for workflows that involve many individual volumes which do not have any boundary behavior. The knowledge that rays will not reflect or refract at the boundary of a volume allows the renderer to perform significant optimizations over the set of many such volumes.

In the Luca cloud scene shown above, several dozen individual cloud elements have been layered together into a unified cloudscape. The aggregate volume workflow allow these cloud elements to be rendered efficiently without having to combine them into a single volume, which may be an expensive process external to the renderer.

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