Vulkan Mobile backend: Point lights can appear brighter (duplicated) depending on the camera angle if there is more than one of the same type in view

[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, point lights can appear brighter (duplicated) depending on the camera angle if there is more than one of the same type in view.

In the minimal reproduction project linked below, this can occur with both the magenta OmniLight3D and the green OmniLight3D. This does not occur with the yellow SpotLight3D because there's only one in the scene. If you duplicate the SpotLight3D and move it, you will be able to reproduce this with SpotLight3D as well.

Vulkan Clustered backend (working)

simplescreenrecorder-2021-12-12_22.47.13.mp4

Vulkan Mobile backend (broken)

simplescreenrecorder-2021-12-12_22.46.54.mp4

Steps to reproduce

• Add a MeshInstance3D node.
• Add two OmniLight3D nodes.
• Add one SpotLight3D node.
• Scatter the lights around in the scene.
• Move the camera around, and notice that the OmniLights will appear to flicker in and out depending on the camera position and angle.

Minimal reproduction project

test_vulkan_clustered_vs_mobile_lights.zip