Quote - If you're still getting excessive fireflies that don't go away after a few hours you should experiment with other surface integrators and change the pixel filter to gaussian.

I had a scene this weekend which wouldn't clean up, even after 8 hours, I switched the surface integrator from 'distributed path' to 'direct lighting' and the scene cleared up completely in 2 hours.

Of course it did. The direct lighting integrator is the same as Poser 7 - straight up plain old raytracing camera to surface to light. There is no bounced secondary light in that model. The fireflies are bugs in the bounced light from surface to surface. That's why they talk about decreasing the kD and kS values. All that does is make them less likely - but they still happen.

Don't confuse grain with fireflies. Grain clears up with more samples. Fireflies don't. They're anomalous extreme values that end up in the accumulation buffer and cannot be overwhelmed back to normal even with 10,000 samples. Just as one set clears up, another is created. And if you get just 1 that has a luminance of 1 billion, that will very shortly bounce around and create a few hundred more at .5 billion luminance. It goes downhill from there.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)