I’m currently rendering an animation, and some of the materials get very heavy fireflies, as you can see here : (2048 samples, 0.003 noise threshold, although the more samples there are, the more fireflies)
If just set it to a default material, there are much fewer fireflies (but they are still there)
The mesh is a megascan, with a very basic shader, here it is
You can get fireflies from other sources than your material… for example, you could have a bright light hidden behind a refractive object, and you’ll get fireflies in the rest of the scene.
Hi, thanks for the reply ! Indeed, that could be the case, but I have no refractive objects in this scene at all, and I also disabled all caustics, which should help ?
There is also a clear amount of fireflies on some objects that doesn’t appear at all on objects next to it… Some of those use bump maps, are they more prone to creating fireflies ?
But even then, I can’t understand why it would happen specifically on the one I shared in my first post, which is as simple as it gets
It’s difficult to say just by looking at the screenshots you posted.
Fireflies are an illumination artifact, and everything that interacts with illumination may cause fireflies… That can be reflections, refractions, light sizes and strengths, etc. That means, the whole scene.
Yeah, I’ll try to investigate a bit more and let you know… But there’s definitely some weird things, for example I have a material who caused a ton of fireflies, and when I disabled displacement in the material, they were all gone. To me it seems there are some specific issues, but I was just wondering whether it was a known thing.
The scene being inside means there is quite a bit of indirect lighting going on, which doesn’t help, but I don’t think it explains everything
What is the “angle” value of the sun in its light settings? You haven’t set it to 0, have you?
Does the sunlight come in through a window? Does the window have glass? If yes, have you disabled the glass material’s shadows? In Cycles, light doesn’t travel through glass very well, especially if refractive caustics are disabled. You would have to give the glass a setup like this one to disable its shadows:
Does the sunlight form a small patch of light on the floor / on an object? If yes, what kind of material does that object have? If it’s a smooth material, it could project some fireflies, and they would likely be sent in specific directions, landing on some objects in particular.
If none of this helps, try switching Cycles to CPU and rendering with path guiding enabled. Path guiding can make use of fireflies and complete their pattern. This may help you identify their source.
Those shadows will be completely unaffected by the light source’s angle. Real glass will let less light through at glancing angles. Way I cope with that - in the few times I feel I need to - is doing 1-(layer weight facing → power 5 → add 0.05), maybe to some arbitrary power to account for energy loss due to total internal reflections in real glass.
I’ve also setup light groups, although getting the right result from unassigned lights is kinda complex to setup. This enables me to examine one class or light source at a time; rendered with GPU at fairly low samples and no denoising. The culprit is usually some form of indirect lighting; bounces off walls into dark corners, glass refractions, or even translucent materials. I may choose to fake it instead of bumping up samples.
