Vulkan Mobile backend: FXAA and debanding have no effect when enabled

[Calinou]

Godot version

4.0.dev (2a9dd65)

System information

Fedora 34, GeForce GTX 1080 (NVIDIA 470.74)

Issue description

When using the Vulkan Mobile backend, FXAA and debanding have no effect when enabled in the Project Settings. These should logically be supported, since the Vulkan Mobile backend uses HDR rendering (which allows for debanding to work). FXAA is also supported on any GLES 2.0-class hardware, which includes any hardware that supports Vulkan.

Vulkan Clustered backend

Vulkan Mobile backend

Steps to reproduce

• Add a MeshInstance3D node.
• Set Screen Space Aa to FXAA in the Project Settings. Notice how the mesh's edges appear smoothed out.
• Switch to Vulkan Mobile backend in the project settings (search for back end).
  • Note: The MRP linked below already uses the Vulkan Mobile backend by default.
• Notice that the mesh's edges are no longer smoothed out.

Minimal reproduction project

test_vulkan_clustered_vs_mobile_fxaa_debanding.zip

[mrjustaguy]

Hm, FXAA seems to work when Scaling is not set to 1.0 in Scaling 3d. Works for Debanding too, however it seems the Mobile renderer suffers from something else that's causing issues that Debanding isn't fixing, probably due to lower percision used somewhere

[Calinou]

As of 83d2673, FXAA on Vulkan Mobile still doesn't work on the MRP linked above, but it works on a brand new project:

Debanding is still not effective in the Vulkan Mobile backend as said above, likely due to the precision used being too low. godotengine/godot-proposals#4193 could address this.

Testing project: test_fxaa_vulkan_mobile.zip

---

Hm, FXAA seems to work when Scaling is not set to 1.0 in Scaling 3d. Works for Debanding too, however it seems the Mobile renderer suffers from something else that's causing issues that Debanding isn't fixing, probably due to lower percision used somewhere

The above MRP uses the default 3D scaling options:

[EzraT]

I can confirm this issue is still present in v4.3.dev5.official [c9c17d6].