* Multithreaded volume light cache
While the render process itself is multithreaded, the light cache pre-process
previously wasn't (painfully noticed this the other week rendering on some
borrowed octocore nodes!). This commit adds threading, similar to the tiled render -
it divides the light cache's voxel grid into 3d parts and renders them with the
available threads.
This makes the most significant difference on shots where the light cache pre-
process is the bottleneck, so shots with either several lights, or a high res light
cache, or both. On this file (3 lights, light cache res 120), on my Core 2 Duo it now
renders in 27 seconds compared to 49 previously.
http://mke3.net/blender/devel/rendering/volumetrics/threaded_cache.jpg
be1d06a2c5
