* Now it's possible to render with the camera inside a volume. I'm not sure how this goes with overlapping volumes yet, will look at it. But it allows nice things like this :)
http://mke3.net/blender/devel/rendering/volumetrics/clouds_sky.mov
* Sped up shading significantly by not doing any shading if the density
of the current sample is less than 0.01 (there's nothing to shade there anyway!) Speeds up around 200% on that clouds scene.
* Fixed a bug in global texture coordinates for volume textures