OpenGL: SpotLight3D shadows occasionally use the wrong texture after moving the camera away from them

[Calinou]

Tested versions

• Reproducible in: 4.3.dev 5708a3a

System information

Godot v4.3.dev (5708a3a) - Fedora Linux 39 (KDE Plasma) - Wayland - GLES3 (Compatibility) - NVIDIA GeForce RTX 4090 (nvidia; 545.29.06) - 13th Gen Intel(R) Core(TM) i9-13900K (32 Threads)

Issue description

When using the Compatibility rendering method, SpotLight3D shadows will occasionally start using the wrong texture after moving the camera away from them. This can be seen in the editor:

compatibility_shadow_error.mp4

Once the SpotLight3D starts using the wrong texture, this is permanent: reloading the saved scene or toggling shadows on the SpotLight3D won't fix the issue.

It seems the SpotLight3D uses the directional shadow map instead of the positional shadow atlas. This is made evident by the fact that once you enter this glitched state, hiding the DirectionalLight3D will also hide the SpotLight3D:

Working	Broken

(The SpotLight3D node has visible = true on both screenshots here.)

No errors are visible in the output log. I haven't managed to reproduce this issue on Forward+ or Mobile, so I assume this is Compatibility-specific.

Steps to reproduce

• Create a 3D scene with a DirectionalLight3D that has shadows enabled and a SpotLight3D that has shadows enabled.
  • An OmniLight3D with shadows enabled may be necessary to reproduce the issue as well, but it might not actually be required.

Minimal reproduction project (MRP)

truck_town_compatibility_shadow_error.zip