Graphic artifact when environment Glow is turned on

[kubecz3k]

Godot version:
3.0.1, but the issue is present in 3.0 as well

OS/device including version:
Ubuntu 17.04, gpu: GTX1060

Issue description:
I noticed that rarely in my game some elements are starting to shine for one frame when camera is moving around, after investigation it turns out that it's caused by GLOW in environment node. I was able to record short gif of it with still camera:

the effect is immediately appearing/disappearing if I move camera in any direction, it's the most noticeable when camera moves (one frame brightness), but it's impossible to capture it in such motion on gif

Steps to reproduce:

1. For the most visible effect download reproduction project (little modified materials demo). Or alternatively you can open material demo and turn GLOW on in environment node.

Minimal reproduction project:
https://www.dropbox.com/s/ga20u9qq9vpbf84/MaterialTesterGlowArtifacts.7z?dl=0 (file to big to upload on github)

[reduz]

This usually happens due to specular blobs.. maybe I should add something to limit specular strength in some materials.

[clayjohn]

I think this is fixed in 4.0 already. Realistically it is not something that can be "fixed" but the impact is reduced by improvements to specular aliasing (roughness limiter and FXAA) and to the glow effect itself.

[clayjohn]

Fixed by #54409

[Calinou]

For people finding this issue via a web search, note that a variant of this issue still exists in 3.x: #15756