Decrease the default number of SDFGI cascades to 4

[Calinou]

Follow-up to #49738 and #54677.

This improves rendering performance noticeably, especially when the camera moves fast. The SDFGI detail remains identical otherwise.

On a medium-sized test scene on a GTX 1080 in 2560×1440, going from 6 to cascades saves 0.5 ms of frame time while looking visually identical (as most of the scene fits within the 4 cascades).

For particularly large scenes, there are still benefits to using more cascades. However, there is no visual benefit to using lots of cascades in small/medium-sized scenes.

Testing project: test_sdfgi_performance.zip

Preview

Before

After

There is a small difference if you look outside the window, but it won't be noticeable in most situations.

[fire]

Out of the box, I would like to have SDFGIs on by default.

By making the default of 4 or even 1 SDFGI cascade will help Godot Engine look more physical and more aesthetic of the box.

[Calinou]

Out of the box, I would like to have SDFGIs on by default.

I don't think enabling SDFGI by default is a good idea for a few reasons:

• SDFGI is still too slow for older integrated graphics (anything older than 11/12th generation Intel Iris Xe).
• Stylized games generally don't need GI.
• If you use LightmapGI or VoxelGI, you should generally disable SDFGI. If SDFGI is enabled by default, then many people will forget to do that and suffer from low performance.
• SDFGI has a cost even if no meshes use the Static bake mode.

However, you can already enable SDFGI quickly in the 3D editor environment preview:

In general, I think Godot should strive to make users only pay the performance cost for the features they actually use 🙂

[akien-mga]

Approved in PR review meeting.

[akien-mga]

Thanks!