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This enables or disables the computation of opacity for transmissive materials (like glass). Leaving it off can speed up a render for possible draft or preview renders.

Presence / Opacity Cached 

Whether the renderer should cache presence (and opacity) or not. Caching these properties will lead to faster tracing, especially for shadow queries, but can lead to a less sharp result than uncached presence/opacity. (Note that checking either subsurface or interior computation will automatically disable presence/opacity caching.)

Computer Subsurface

This enables or disables the computation of subsurface scattering (when in use). Leaving this off can speed up draft or preview renders.

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