Scale AO, Normals intensity by distance

[MopanionStudios]

Addresses #857

You can close this pull request if you like, as I understand I am not assigned to the issue, but I implemented a lightweight method using Xstarsia's plan to use dFdx/dFdy space for scaling the AO and normals intensity depending on their distance to the camera.

I allow for the effect's intensity to be adjusted by a shader parameter, and clamp it to 1.0 at minimum so that it doesn't go below the normal depth / ao original values. It adds a subtle but noticeable difference that improves the visuals, as seen here:

[MopanionStudios]

Just updated/fixed the distance scaling, before it was utilizing UV space which goes from 0-1 in regions. To make the scaling more reliable, it now uses v_vertex, I also changed the name of the uniform float controlling the effect to make its purpose more clear. Heres an updated example of what the effect does:

2025-11-22.12-26-25.mp4