Modified this post 2012/6/21

I have posted images of particles. It might be interesting to use this one.

"Noise Reduction for Path Traced Imaging of Participating Media" (http://www.eurasip.org/Proceedings/Eusipco/Eusipco2011/papers/1569426055.pdf).

Another thing I would like to mention is about "Accelerated Light Propagation Through Participating Media"(http://isg.cs.tcd.ie/cosulliv/Pubs/LeeLightProp.pdf).

I found a little mistake in updating

*pos*. I think it has to be

pos = pos + dir x

*( -log(u) / (sigma_a+sigma_s) ).*
The authors terminate a ray if

*ta < ts*, which I thought was interesting. The parameters*ta*and*ts*are given as*ta = -log(u1) / sigma_a*

*ts = -log(u2) / sigma_s.*

However, a little calculation shows that this is exactly the same as performing Russian roulette with

*sigma_s / (sigma_a + sigma_s)*so there is no need to compute*log()*every time.