Add export settings to the export dialog for GLTF

[aaronfranke]

Describe the project you are working on

I am working on a Godot game with dynamically loaded assets, mostly GLTF files. These assets can support many advanced extensions exported from Godot, like the OMI physics extensions.

Describe the problem or limitation you are having in your project

In addition to importing GLTF files into our game, we need to provide users with a way to create those files. Fortunately Godot has a GLTF exporter in the editor, and we can allow Godot to export advanced extensions like OMI physics.

However, sometimes when exporting from Godot, the file size they take up is simply too big. One easy way to reduce the file size is to change the image format to one with a lower quality setting, but this is currently not possible to do, since the GLTF exporter has no options and is currently limited to only exporting PNG files.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

The proposal is to add a menu to the GLTF export dialog to allow configuring export settings. These are things that would not be in the Godot scene pre-export, but need to be specified at export time. An easy one would be setting the copyright string. And of course, solving the limitation of this proposal: setting the image format.

However, we don't have to just hard-code a few settings. We can open this up to allowing GLTFDocumentExtension classes to provide export settings, so that any extension can be configured at export time.

For the visuals, we can take inspiration from the similar settings in Blender's export menu:

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

PR: godotengine/godot#79316

If this enhancement will not be used often, can it be worked around with a few lines of script?

It can't be worked around with a few lines of script, and exporting GLTF files will be used quite often.

Is there a reason why this should be core and not an add-on in the asset library?

GLTF support, including export, is a core feature and an editor feature. Also, this proposal opens the door for add-ons in the asset library to provide their own export options.

[adamscott]

Discussed during the animation/asset-pipeline team meeting:

• there should be support for .jpg;
• there should be a way to preserve the exact bytes of the original image files;
  • like, import PNG, but if there's a JPG file, keep the JPG file as is.
• the editor inspector should be usable by other file formats other than GLTF;

[roundabout stand in]

[akien-mga]

Implemented by godotengine/godot#79316.