[3.x] Add a Preview Bake button for quick iteration with BakedLightmap

[Calinou]

• 3.x version of Add a Preview Bake button for quick iteration with LightmapGI #80518.

When using the Preview Bake button instead of Bake Lightmaps, low quality settings will be used instead of settings from the BakedLightmap node. A node configuration warning will be displayed besides the BakedLightmap node to inform the user that the bake was done in preview mode. This preview bake warning is persisted to storage to make teamwork easier.

This helps iterate quicker on a scene's lighting since you don't need to wait as much time to see results.

On a simple test project, Preview Bake (0:00:38) was about 3 times faster than a "final" bake (0:01:48) with the default BakedLightmap settings.

By default, Preview Bake uses:

• Low quality for baking.
• 1 bounce, unless the BakedLightmap node is set to 0 bounces (in which case it uses 0 bounces as well).
• Low quality for dynamic object capture.
  • You can disable dynamic object capture entirely in the Project Settings if you don't need it for previewing purposes.

The preview bake settings above can be adjusted in the Project Settings. These are project settings so that different team members always use the same preview settings for consistency.

Comparison between Preview Bake and "final" bake

• This addresses Add a "Preview Bake" button for BakedLightmap for quick preview bakes godot-proposals#2029 for the 3.x branch.

[Zireael07]

If I understand it correctly, I can use preview bake if I want to in production (because real bakes will likely take too long on my hardware), this is just a suggestion/reminder?

[Calinou]

If I understand it correctly, I can use preview bake if I want to in production (because real bakes will likely take too long on my hardware), this is just a suggestion/reminder?

Yes, the preview bake is still saved and can be used in an exported project. That said, for your use case, I'd recommend you change the BakedLightmap node properties instead of relying on Preview Bake.

[Calinou]

I rebased and moved the preview_bake property to BakedLightmapData as requested by @JFonS. I tested it again, it works as expected 🙂

Maybe we could even add a .preview. infix to the saved file name, so baking in preview mode doesn't overwrite a "final" bake you may already have.

I'm not sure how to handle that part without accidentally exporting those preview bakes in the final PCK (if they weren't removed by the user). I think preview bake data could even be stored in .godot/, but I'd leave that for a future PR.