[Bf-committers] Volume Rendering Updates

[Aurel W.]

Hi,

a couple of months ago I played around with blender volume renderer
and made some additions and also fixes. I needed a very special and
easy type of volume rendering back then for a project and I based this
on blenders volume renderer. I think part of my work could be also
useful to others.

Some of the fixes and changes I have made back then were communicated
to Matt and are partly in trunk. But most of the stuff isn't and keeps
passing by. So before this gets completely obsolete and before I loose
the last remaining bit of interest in it, I might wonder, if it would
be appreciated to contribute this.

Some of my changes:
* Smaller fixes
* Better alignment of the single scattering radiance cache (also
called light cache in blender)
* Self shadowing with bounding geometry
* Stochastic multiple scattering, based on single scattering radiance
cache (only isotropic scattering)

Changes which still need work/reimplementation:
* Caching/Baking of radiance caches
* sigma_s for an RGB spectrum, currently only sigma_a can by tinted in
a weird way
* Adaptive sampling for volume ray casting, optimized for cache resolution

I have written a documentation back then, which is full of other
details of the related project and a more general discussion on volume
rendering. But in the volume rendering section, there should be a good
explanation of my work:
http://atommuell.mum.jku.at/~aurel/VolumeScatteringSimulation.pdf

Again, it's really not an advanced multiple scattering technique,
actually quite simple stuff. At the end of the document there are also
some more formal tests, which proof the correctness of the single
scattering implementation by comparing it to analytically solved
scenes.

If there is interest in it, this might be the last chance of me
merging this into blender. Tho I sort of believe that it doesn't mach
much sense to put a lot of effort into blenders internal renderer
these days, It wouldn't be that much work for me to include this and I
can spare some days in February for this ;)

So if there is interest, I would be happy to do a quick branch.

aurel