SpotLight light not working on Android when its Shadow is enabled

[TIBI4]

Godot version:
3.1 beta 3

OS/device including version:
Android/Xiaomi 4A/Adreno 308

Issue description:

• All below in Android export.
• SpotLight is not working when Shadow is enabled (no light, no shadow), but DirectionalLight and OmniLight work as expected with or without Shadow enabled.
• SpotLight works when Shadow is disabled (only light).
• SpotLight should work when Shadow is enabled (light and shadow).

Image from Editor info:
In the back: OmniLights
In the front: SpotLights
In the left: Shadow=on
In the right: Shadow=off

As you can see, in the Editor (runned by F5), in the left SpotLight there is light and shadow, but in the Android export, there is not light or shadow.

Steps to reproduce:

• Export the uploaded .zip to Android.
• Run it on Android.

Minimal reproduction project:
Zipped.zip

[volzhs]

check this #24710

[akien-mga]

check this #24710

As per the above it seems to be expected, can you confirm that you get similar results on Android and desktop if you change the Vertex Shading option?

[Calinou]

#54343 was able to reproduce this even with vertex shading not forced on mobile.

@norrath-hero Can you reproduce this if you increase the SpotLight's shadow bias to a higher value like 0.4? If that still doesn't work, try enabling Reverse Cull Face on the SpotLight then set the bias to -0.1.

[norrath-hero-cn]

Just tried these by "Deploy with Remote Debug" :

1. SpotLight's shadow bias 0.4, 0.8, 1.4, still doesn't work.
2. Reverse Cull Face on and bias -0.1, still doesn't work.

[akien-mga]

Fixed by #69826.