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Things seem to be progressing the exact same way we did in the offline world: start introducing raytracing to capture certain effects that are difficult to get looking right with rasterization techniques, then when the hardware catches up move to full path tracing and do away with the massive ball o...

Very cool! I love the volumetric caustics in the lens image.

One thing that I realized is that when the random selected light happens to be behind the point that is being evaluated the potential contribution is 0, and therefore the sky will be selected with a probability of 1. However, another light may in fact be visible, so when I stumble upon it the MIS p...

Yeah I think CMJ performs pretty well from what I've seen, but still suffers from the limitation that you've got to know your sample count up front.

I just tried halton this afternoon and found it to be slightly worse than sobol in a naive implementation. I also looked at your code and tried reordering the low dimensions as you do but found that gave me more noise than the default ordering. I think I need to spend some more time tweaking the imp...

Actually looking back at my code, both examples were with 1024 samples. At 4096 samples the 14,15 space is completely covered, although I think the 24,25 space needs 8192 samples to be covered. How does the Faure-permuted Halton perform at lower sample counts?

That does look a lot better, I'll give it a go, thanks! Does it have any bad 2d projections in other dimensions?

Thanks toxie. After thinking about it some more I'd sort of realised that was the case. I guess in the limit then the sequence explores the whole sample space in a nicely-distributed fashion, which isn't necessarily what I'm after.

What's considered "state of the art" these days?

In the BeckmannSample11 function in microfacet.cpp you have special logic to check for whether we're at normal incidence and sample the slope directly, but then the rest of the function continues as normal and *slope_x and *slope_y will be overwritten. Shouldn't the function return after line 48? ht...

I have a Maya shaderball scene you can use as a starting point here (scroll down to the bottom of the page):
http://anderslanglands.com/alshaders/

It's set up for Arnold but should be easy to adapt for your purposes