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Eevee rendering "fireflies"
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Description

System Information
Operating system: Windows 10 64-bit
Graphics card: Geforce GTX 970

Blender Version
Blender 2.8
Date: 2018-12-22 00:52
Hash: dafaa6f22881
Branch: blender2.7

Short description of error
I'm getting these white pixels/squares/rectangles in my Eevee renders. I've only ever seen it occur on top of particle hair and card-based hair with "hashed" transparency.

During an animation it will only happen on certain frames, and assuming nothing is changed will always appear on that frame when rendered.

The artifacts always seem to be either 1x1 pixel, 1x2 pixels, 2x2 pixels, or 6x8 pixels, and can be affected by depth of field, bloom and other effects probably. One of the frames I've rendered has a blurry white blob about 140x140 pixels.

Exact steps for others to reproduce the error
This is very frustrating because it's happening in a "production" file with many commercial assets so I can't upload the file. I also haven't been able to reproduce it in a simple file. I may be able to trim the file down if necessary.

Event Timeline

A sample file would be invaluable, even if it’s just the Suzanne head in those screenshots. Does increasing the samples affect it?

I'll start trimming the file down so I can upload it.

Concerning sampling:
In this specific case the artifact only starts to appear at 94 render samples, and is still visible up to 2000 samples at least.

In another test with a production character it starts to appear at 19 frames.

I managed to reproduce the artifact in another file.

I currently have DoF enabled which will blow it up but it starts as a single pixel.

It probably happens on other frames but it first occurs on frame 3. It appears at 2 render samples.

I get the same thing in an Eevee render. As Brendan notices, it's worsened by dof and bloom. In my case it seems to be specular highlights..

Here's a link to the file: https://www.dropbox.com/s/yjs9q1oi95mqoqy/scenetest.blend?dl=0

It's a scene for a tutorial in 3d world magazine about VR sculpting.

I reproduced this under the following circumstances (file attached):

Two faces with an overlapping edge and an edge split modifier assigned. The object has an Principled BSDF shader in its material. No Fireflies. Now you add an normal map node (TANGENT SPACE) and connect it to the normal slot of the BSDF node. Fireflies appear on the overlapping edges. I figured out that the firefly comes from the sheen component in the BSDF shader:

https://developer.blender.org/diffusion/B/browse/master/source/blender/gpu/shaders/gpu_shader_material.glsl$1094

If you clamp this f value to a -1 to 1 range the fireflies disappear.

Brecht Van Lommel (brecht) lowered the priority of this task from 90 to 50.

I've been having the same issue with architectural models exported from CAD software. A lot of CAD models are, shall we say, 'liberal' with their geometry - there are often a lot of overlapping edges. Where multiple edges overlap, I get fireflies (even with all shader values at default + no maps). Moving or collapsing the extra edges gets rid of the fireflies, but this is very time consuming to do with every problem surface.