Specular aliasing becomes more visible when depth of field or glow is enabled

[lukaskotik]

Godot version:
Godot 3.0 rc1 official

OS/device including version:
Ubuntu 16.04 64 bit
GeForce GTX 750 Ti, NVidia driver 384.111

Issue description:
Graphical artifacts are visible (for some viewing angles and zoom levels) when Dof Far Blur or Dof Near Blur in environment is enabled. These artifacts are placed in the areas of "high" reflections (see images).

Steps to reproduce:
Open 3D material_testers demo, enable Dof Far Blur and Dof Near Blur, try to zoom in/out, rotate camera. Make the same in the running scene. (artifacts are visible both in editor and in running scene).

Artifacts:

Blur off:

Blur on:

Minimal reproduction project:

[reduz]

This is technically not a bug, just the shape of the filter because the resulting specular lobe at this size is very strong. Maybe specular could be clamped or eventually be applied after tonemapping. Easy fix for now is changing roughness from 0.02 to 0 or 0.05 (a bit bigger)

Will mark as enhancement for 3.1

[lukaskotik]

It's quite irritating shape of the filter - see the first picture or the most right artifact in the last figure. Anyway I played with settings of environment and I can't get rid off these white rectangles (without affecting the blur effect). What do you exactly mean with "changing roughness"?

[AndreaCatania]

roughness of spatial material on the single mesh

[lukaskotik]

Thanks! Setting it to 0 removed the artifacts (together with the reflection). With higher values the artifacts still occur.

[akien-mga]

Is this still reproducible in the current master branch? What about the GLES2 backend?

[Calinou]

I can still reproduce it on commit 35c1694 with the default parameters (roughness 0.02):

Setting the material's roughness to 0 solves the issue, since the specular blob doesn't appear anymore. Also, depth of field isn't supported in GLES2, so the issue doesn't apply there.

[akien-mga]

Still reproducible in 4163419:

WIth higher roughness I get artifacts in other locations (foot):

[akien-mga]

Still reproducible in 3.3-stable. CC current @godotengine/rendering contributors in case you want to poke at this one :)

[Calinou]

Note that this is most likely not reproducible in the master branch since it has a new DoF implementation with proper support for bokeh.

[clayjohn]

This is a form of specular aliasing resulting from the high intensity of the specular lobe.

To fix these sorts of artifacts what we need to do is convert the buffer to LDR before performing the blur operation then convert back to HDR after blurring. We should do something similar with Glow to reduce specular aliasing.

[Calinou]

This was fixed for glow in master by #54409. I haven't checked if this applies to depth of field in master yet.

[clayjohn]

Right now it was just added for glow, but the same concept applies for DoF.