I'm working on an animation where a cube of jelly falls from the sky (it's best not to think too hard about it).
There are loads of speckles, which I've learned are called "fireflies" from this post. I tried the despeckling suggestions at its referenced link, but each of them has a pretty serious problem.
For instance, if I turn off caustics, the fireflies disappear, but the bottom plane of the jelly where it contacts the floor turns black. It only makes sense, I guess; blue filtered through red would be black, and if there are no caustics, light can't bounce to the floor.
I've also tried making my lamps bigger, which does make the bottom more visible, but the fireflies are just less bright, and the shadows fade too:
Ugh. Other things I've tried:
- Increased the render Sampling samples to 1024; no help. I accidentally set the preview samples to 0, and came back in 3 hours or so; it had reached 30K samples and the fireflies were gone, but c'mon, 3 hours?
- Increased the render Light Paths transparency and bounces. I've tried lots of combinations, I can't even remember them all. Mostly increasing max, diffuse, and transmission (the cube has no glossy or volume shaders).
Could someone explain where these fireflies are coming from, and how to get rid of them without losing my shadows, my bottom transparency, or my render time?