Vulkan: SDFGI does not make the editor redraw until it has fully converged

[Calinou]

Related to #62887.

Godot version

4.0.dev (c89061e)

System information

Fedora 34, GeForce GTX 1080 (NVIDIA 470.74)

Issue description

SDFGI does not make the editor redraw until it has fully converged. This means that when toggling SDFGI or changing a setting that causes it to regenerate (such as changing the number of cascades), it will have partially-converged appearance until you move the 3D camera around a bit (or cause the editor viewport to update somehow, e.g. by hovering controls).

In #53353, we resolved this by making the editor redraw continuously when a FogVolume is visible and volumetric fog with temporal reprojection are enabled. This isn't an ideal solution, as it wastes CPU and GPU resources (which in turn decreases battery life on laptops). Nonetheless, it prevents the 3D rendering from mismatching how the running project will look like.

Ideally, we should resolve this by redrawing for rendering/global_illumination/sdfgi/frames_to_converge frames (30 by default) whenever a SDFGI update is requested in RenderingServer. We can then stop redrawing once SDFGI has fully converged.

sdfgi-updates-only-when-redrawing.mp4

Steps to reproduce

• Add some MeshInstances with their GI Mode set to Baked.
• Add a WorldEnvironment node with a Environment resource.
• Enable SDFGI, but don't move the 3D editor camera afterwards for a bit.
• Start moving the 3D editor camera.

Minimal reproduction project

test_sdfgi.zip

Keywords for easier searching: low processor mode, low-processor mode