Godot: GLES2 shading issue

[kaadmy]

Godot version:

Godot 3.2 beta 1, GLES2 renderer

OS/device including version:

Motorola G4 (Android 7)

Issue description:

Serious fragment shading issues on surfaces.

Steps to reproduce:

1. Create a GLES2 project
2. Add a MeshInstance with a default sphere shape
3. Give the MeshInstance a material with very low roughness (I used 0.06, any value will work but lower roughnesses have more visible issues)
4. Place a camera very close to the sphere (As close as you can, keeping the sphere on screen)
5. Export for Android and run on your device

Minimal reproduction project:

gles2_fprec.zip

[kaadmy]

There is already an open issue for this in the Godot Oculus mobile repository, but since I can reproduce it on a regular Android device the issue is more relevant here.

[clayjohn]

CC @NeoSpark314

[NeoSpark314]

This is related also to https://github.com/godotengine/godot/issues/32813 (and https://github.com/GodotVR/godot_oculus_mobile/issues/60)

This is a floating point precision issue due to the fact that medp is using 16bits. Some more details are in the oculus mobile issue https://github.com/GodotVR/godot_oculus_mobile/issues/68 including a small performance benchmark of enabling high precision for all computations on the oculus quest. @clayjohn suggested in a discussion on discord that the agreed solution is providing a project setting to enable high precision.
I will look into creating a PR for this.

[avril-gh]

look at the spotlight shadows images in https://github.com/godotengine/godot/issues/33551

[kaadmy]

I just tried forcing high precision locally (same method as the PR above), and this issue still persists, albeit in a slightly different form.

[NeoSpark314]

@kaadmy can you try disabling in the project quality settings the mobile approximations like shown below?:

[NeoSpark314]

@kaadmy I was able to reproduce the issue now also on my oculus quest. Changing the settings did not help. The precision fix in the PR gets rid of the noise; but the dark reflections seem to be an additional issue not fixed by the precision increase.

[kaadmy]

Same issue occurs here, I've also tried disabling all shading options to no avail. I'll try fixing it locally since I can easily reproduce the issue.

[NeoSpark314]

I think I found the cause of the issue: Mip Map level 1 of the prefiltered sky environment map is black!; all other mip levels look correct: here is a render doc trace from the quest with the mip levels visualized:
Mip 0, 1, 2:

[kaadmy]

I tried disabling mipmap generation (always source from panorama texture and don't blur) and I seem to get much better results:

This is with the default precision (mediump), highp looks very similar but still has some shading discrepancies.

[Calinou]

@NeoSpark314 Sorry to interrupt, but since you seem knowledgeable about mipmapping, would you know if it's possible to fix #33519 without too much trouble?

[akien-mga]

Fixed by #33646.

[eastrd]

Hi, this issue still seems to persist under both 3.2.2 and 3.3.3, tested on Oculus Quest 2.

[Zireael07]

Please open a new issue, as it's likely something in the VR code.

[akien-mga]

@eastrd It's fixed in 3.2.3 (3.2.2 was released long before this issue was closed).
You have to enable a setting to use it, see #33646.

[Filippopotamus]

The issue still remains in 3.2.3, even when setting the high precision float flag. It goes away if I change the WorldEnvironment to be Color. But if it is set to Sky or Sky+Color, the issue is still present. Our project is not VR related. Just a regular Android GLES2 app.

[akien-mga]

Please open a new issue with a reproduction project.

[Filippopotamus]

@akien-mga issue created: https://github.com/godotengine/godot/issues/43667