Allow any number of frames for the SDFGI Frames To Converge setting

[Calinou]

This allows for more flexibility over the stability versus update speed compromise.

This closes #50773.

Preview

Edit: This pull request was amended to limit the maximum value to 120 (instead of 300). Higher values don't bring a significant benefit, but make performance drops more extreme when the camera moves fast.

Bounce Feedback 0, Energy 1

Default (25 frames)	Maximum (300 frames)

Bounce Feedback 0.5, Energy 0.5

Default (25 frames)	Maximum (300 frames)

[clayjohn]

I don't think this closes #50773. 300 frames to converge would take 5 seconds at 60 fps. That would be totally unusable for a camera in motion.

To close #50773 we need to improve SDFGI so that it is less blotchy at reasonable settings.

[Calinou]

That would be totally unusable for a camera in motion.

From my testing, it seems to work well enough if the camera doesn't move too fast. The usability of higher values also depends on your cascades' individual size (which is determined by the Cell Size property). With larger cell sizes, GI will be less detailed but a given cascade will cover a larger area, which reduces the need for SDFGI generation when the camera is moving.

[Calinou]

Rebased and tested again, it works as expected.

Note that I decreased the maximum value from 300 to 120, as values above 120 don't bring much of a benefit compared to the performance drop caused by fast camera movement.

As an added sidenote, #56761 makes very low frame convergence numbers viable if you combine it with a high SDFGI Probe Ray Count setting. You can get fully real-time GI in a way similar to VoxelGI, but with SDFGI 🙂
The added bonus is that fast camera movement will barely cause any slowdown.

[reduz]

I will entirely change this code when I get a bit more time, so feel free to close this one.