[3.x] Add a setting to reduce dark SSAO artifacts when the camera gets close to materials

[Calinou]

Follow-up to #53784.

This setting clamps final SSAO intensity. With this setting correctly configured, SSAO artifacts will still occur, but they'll be much less noticeable.

The default value is 1.0, which means the existing behavior is unchanged.

This closes godotengine/godot-proposals#3720.

Testing project: test_ssao_3_3.x.zip

Preview

ssao-max-obscurance-setting.mp4

Scene 1

Before	After (Max Obscurance = 0.5)

Scene 2

Before	After (Max Obscurance = 0.5)

[clayjohn]

I think users should be able to set their AO to black if they want.

We should solve the bug that causes SSAO to become unnecessarily dark when the camera approaches a surface instead.

If you are only interested in a stopgap solution, then a configurable max should be exposed like in 4.0:

godot/servers/rendering/renderer_rd/shaders/ssao.glsl

Line 445 in d956904

obscurance = min(obscurance, params.shadow_clamp);

note: in the attached code, we are dealing with obscurance so a min function is used

[Calinou]

If you are only interested in a stopgap solution, then a configurable max should be exposed like in 4.0:

I added a setting for this. It requires increasing the number of binder arguments from 13 to 14, which means the diff is large compared to the feature itself.