No more Fireflies

I found a very good way to delete fireflies. …yes, it was more an accident ^^
But it works realy powerful!

So: If you work with separated Renderpasses,
you need to use the “Math”-Node in “Diffuse Indirect” and “Glossy indirect” BEFORE you
mix all the passes together. Just put die Output from this passes to all inputs from the Math-Node.
(One Math-Node for both Nodes separate) and set the Math-Node to “subtract” Thats it!

I was having a Lot of fireflies here in this exsample. But, like magic, they are all gone with the
trick i’ve writen here :smiley:

Here the Fotos from my project:

and without fireflies:

That’s cool, what? I’m sooo happy to found this. ^^

(I know, the electricity looks not the same like before, but this is, because i used the blur-node on the emit-pass - it has
nothing to do with the fireflies…)

Good! Very good! Thks!

If you subtract anything from itself, you get black. So you’re right, no fireflies, but this is screwed. You could’ve used a RGB node instead.

These highlight dots are caused by too sharp reflection combined with too small light source. Either do some compromise regarding the metal material or create a fake light source that would be larger and dimmer.

That’s great to know, thank you! I allways wonder, how this fireflies are coming in to the picture…

Yes I’m ok with Emu, is it because your background is black?
You must make tests with a clear scene to be convinced, right?


Yes, Testing is a good idea. I’m just very happy, because it works here, in this work so great.
But in later Projects, i promise, i test this idea again and again and again.
And then i post here on Blenderartist, what my experience is.

How i understand this now: Fireflies are a problem in the compositing. And the Trick with the math-node is fixing that
I can’t see any other point, why the fireflies are gone - and the rest of the picture looks the same. Possibly, the fireflies turn to black - but i don’t think so. Lets see what the future brings ^^

Till’ then.

they added a feature long ago called clamp… it is very effective for fireflies. not to be confused with noise removal

Wait a minute, what you are doing is actually subtract the passes from themselves to black! This works in this scene only because you don’t need them (direct lightning), but in a real indirect light scene that areas would be black.
Your node setup is: Pass > subtract from same pass > out which equals BLACK. You can easily see this in the preview node with that pass only.

You could also not connect them at all instead, and have only the direct diffuse+emission (which is firefly free)
Use clamp or a smart light setup like odin and emu said.

Absolutely… you are all right :slight_smile: I was wrong. It did just work veeery good in this scene.
Later, i did test it in an other Scene and yes, the fireflies are gone, but how enilnacs wrote,
the picture was no longer correct…

Thank you all for answering! Now i understand much more about this theme.

To get rid of fireflies, use either this absolutely great (and free) tutorial from Bartek Skorupa:

Jump to the point where he talks about firefly removal, the tutorial covers A LOT of different stuff.

Or use a clamp value (which i personally don’t recommend > affects textures!). :stuck_out_tongue: