BaseMaterial3D distance fade dithering exhibits checkerboard pattern when TAA is enabled

[Calinou]

Tested versions

• Reproducible in: 4.0.4.stable, 4.1.4.stable, 4.2.2.stable, 4.3.rc e343dbb

System information

Godot v4.3.beta (e343dbb) - Fedora Linux 40 (KDE Plasma) - X11 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4090 (nvidia; 555.58.02) - 13th Gen Intel(R) Core(TM) i9-13900K (32 Threads)

Issue description

When you move towards or away from a material that has BaseMaterial3D distance fade dithering (either Pixel Dither or Object Dither), you can see a checkerboard pattern appear:

dither_taa.mp4

This pattern's size is resolution-dependent, but its size also depends on your movement speed. Depending on your movement direction, its shape may also change (it'll be purely horizontal lines if moving exactly sideways).

dither_taa_moving_in_3d_editor.mp4

This pattern is hardly visible with FSR2 in comparison:

dither_fsr2.mp4

Steps to reproduce

• Use the Forward+ rendering method (required for TAA to work).
• Enable Use TAA in the Project Settings.
• Create a MeshInstance3D with a BoxMesh, and add a StandardMaterial3D with Distance Fade > Pixel Dither enabled on it. Set the Min Distance and Max Distance so you can see the dithering pattern over a large distance.

Minimal reproduction project (MRP)

test_taa_dither_checkerboard.zip