SSR artifacts

[Zireael07]

Godot version:
3.0.2

OS/device including version:
Radeon 6630M
Windows 7 x64

Issue description:
I get weird artifacts when SSR is on. No amount of fiddling with SSR setting helps.

https://webmshare.com/0BXw1

(The artifacts are: horizontal lines on car window with chase cam and the flashes of ... something... on the apex with interior cam)

Steps to reproduce:

Minimal reproduction project:
Probably difficult to repro in a minimal project, as I'm guessing it's related to amount of geometry in scene.

[LinuxUserGD]

#14837 ?

[Zireael07]

The artifacts are not black - I think they are the sky color, blueish at any rate. And I run 3d, not 3d without effects.

[Zireael07]

It's been months and I saw similar artifacts in 3.1 alpha 2, but this time, the inspector is a bit nicer and I was able to figure out the cause. It's not transparent meshes, unlike what I originally thought. It's the roughness checkbox in SSR in combination with the label I have above the car (the letters are fairly thin and they (or any similarly thin things on screen) end up as vertical or horizontal artifacting lines).

Unticking the roughness checkbox was the only thing that helped - no amount of fiddling with other parameters and/or material roughness itself helped.

I am not closing the issue since it seems to point at a problem with the roughness parameter of the SSR.

[Zireael07]

#25112 has more details and pics, so closing.