ompf2.com

A very easy and relatively robust solution is to only clamp the final pixel contribution to some maximum value, say 10. This way you make sure that a single VPL cannot contribute huge amount of energy (either due to low PDF, due to landing around a corner, or due to a sharp BRDF). This parameter is...

I also have a code that does RGB <-> spectrum conversions in my gpusppm:

http://cs.au.dk/~toshiya/gpusppm.zip

I've tested the code and it should be fairly accurate in the sense that RGB -> spectrum -> RGB well recovers the original RGB value. It's based on that paper with some improvement.

The correct order is, accumulation, tone mapping, and then gamma/color correction. You can think of accumulation of spectral contributions as a part of Monte Carlo integration, which should be done before any image processing like tone mapping and gamma correction. Having said that, if you can easil...

You can see this approach in action in my gpusppm :-> Anton is right that this approach is prone to banding artifacts. However, with enough samples (to the extent that the purely random approach also converges), I don't necessarily find this correlated approach inferior. Theoretically, both have the...

Can't you just turn it into two dimension by randomizing a common time and wavelength for each pass? I thought it was standard practice for sppm class of algorithms. I'm probably missing some important details.... That's how I did motion blur in SPPM, and it also works fine for spectral rendering. ...

But that's what is visible in the pics though.. (and the pics that don't show it, have been run for a very long time) You are right. Maybe my question is whether directional blur has some good properties for the combination with MCMC which spatial blur does not have. From http://igad2.nhtv.nl/ompf2...

VCM = vertex merging + BPT, that's why I claimed it outperforms (S)PPM. Sorry for my misunderstanding :-> SPPM \approx VM (vertex merging) and VCM = VM + BPT indeed. Another difference to note here is that the MCMCPPM does still employ path reusing, whereas Anton's modified MLT does not. Therefore,...

I wonder why you do not run into the problem of very high variance of BRDFs? Even though mollification essentially blurs out the delta function of specular materials, wouldn't it still result in a very large value (or very small value) when you apply this idea to connection paths?

BTW, VCM seems like a very great GI algorithm! Is it the current state of the ait, out performing SPPM, MLT? It definitely outperforms SPPM, but not necessarily MLT. The last path space regularization paper of Anton Kaplanyan shows a kitchen scene where MLT can outperform VCM. It's a rather extreme...

I just want to add that we are also planning to release an example code for our paper ""A Path Space Extension for Robust Light Transport Simulation", which basically results in the same algorithm as VCM :-> Our code will not be as fancy as ingenious', but I hope it will further help people to under...