Metropolis Light Transport and stuff.

Hi!

Long time no see. Like always I was rewriting it from scratch a couple of times. But nevertheless it's still java and now it uses metropolis sampling to help that poor path tracing converge.

Btw. I did MLT on yesterday evening after 2 beers (it had to be Ballmer peak).

Altough the implementation is still very fresh it easily outperforms standard path tracing, what is to be seen especially when difficult caustics are involved.

I've implemented spectral rendering too, it was very easy actually, cause all computations on wavelengths are linear just like rgb. But then I realised that even if it does feel more physically correct to do so, whats the point? 3d applications are operating in rgb color space, and because I cant represent a rgb color as spectrum interchangeably I have to approximate it, so as long as I'm not running a physical simulation or something I don't see the benefits (please correct me if I'm wrong), thus I abandoned that.

I was also working on dispersion (rgb rendering), but that feature needs a little more work (I've included an old pure path tracing rendering with dispersion visible)

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