Godot Docs on vrs no longer accurate

[jamie-pate]

This note says:

    The Compatibility rendering method does **not** support variable rate
    shading.

https://github.com/godotengine/godot-docs/blob/master/tutorials/3d/variable_rate_shading.rst?plain=1#L89

But VRS is now supported in the compatibility renderer.

I would update the docs but I don't understand all the limitations of this system.

See also:
godotengine/godot#93685
godotengine/godot#89894
godotengine/godot#80881
godotengine/godot#60901

[Calinou]

As I understand it, the implementation is limited to support in OpenXR, so you can't use an arbitrary texture as the VRS fragment density map. This means the XR mode will work, but not Texture.

cc @BastiaanOlij

[jamie-pate]

To me it should be a full compatibility matrix:

• It works in vulkan
  • on all platforms? desktop only?
  • Unless you enable MSAA
• It works in opengl with OpenXR if you have the facebook extension
  • Android OpenXR compatible devices only?
• Sometimes only it works with texture mode, other times it only works with XR mode
  etc

[BastiaanOlij]

Indeed, on compatibility its a feature of OpenXR and ONLY works in VR situations, not of Godots rendering engine, and it will be disabled in many situations (enabling post effects, screen reading, scaling, etc.). And it is a totally different system from Godots VRS implementation.

The XR docs reflect this already and I feel that is enough. Those who are interested in using VRS outside of XR will only be put on the wrong path.