Converting three.js glb export for use in legacy gltf loaders

[kfarr]

I help maintain an open source A-Frame / three.js web app 3DStreet which lets users create street scenes and offers a feature to export a glb of the user's current scene using three.js GLTFExporter.

For use cases with regularly updated 3D tools like Blender, this works as expected, however many target third-party platforms such as mobile AR viewers only support legacy gltf features (and definitely not texture transforms which we used widely in our app).

The 2 viewers we're targeting are incitu (appears to use ArcGIS mobile SDK) and Adobe Aero (legacy codebase with old gltf loader).

Therefore I'm trying to use gltf-transform to convert the glb output from the raw three.js output into a version that could be used by legacy viewers. Eventually I'd like this to be run in browser as a built-in option for legacy support when exporting, but for now I'm testing out a node script so we can focus just on the conversion step.

I've tried on my own to adapt gltf-transform following example from this thread:
3DStreet/3dstreet-assets-dist@main...test-glb-process-script

The output correctly removes the transform extension, and looks correct on a modern reference gltf viewer, but cannot be opened by legacy viewers (causes errors or crashes) so I assume I must be missing a core step to ensure legacy compatibility in the transform process.

Versions:
A-Frame 1.5 / three.js v158 (in browser)
exporter from three.js v145

Any ideas on how to make this work better? I will try next to upgrade to a more recent version of three.js for both the exporter and our browser runtime. I can also paste in the errors I get from the respective platforms.

Example raw glb export (zipped) for testing conversion and import: 3dstreet-app-raw-glb-export.glb.zip

[kfarr]

For incitu:

• the raw glb export partially works if objects with skeletons are excluded from the export --> that could be an option in our UI.
• the file size approaches the 25MB limit for incitu when vehicles and peds are removed, and could easily exceed that with more complicated scenes. Perhaps downsizing textures, could help? do they support webp? other "basic" optimizations?

For aero:

• for raw glb export, exhibits issue with texture transform like screenshot, but it does allow for rigged models with skeletons
• testing transformed output next -- works as expected!

Aero before / after

[kfarr]

summary of problem / solutions:

• aero does not support texture transform - fixed w/ the test script in this thread 🥳
• incitu does not support skeletons - can be fixed w/ option to exclude vehicles, bikes, and people from export 🚳
• aero does not show texture color on some meshes in a glb - no clear solution / defer this issue?
• incitu has 25mb limit, complicated scene will push over limit - potential to simplify mesh / resize / compress textures

[kfarr]

Ok I got this all working no need for the question anymore :)
Here is our next step to implement this in our app: 3DStreet/3dstreet#1044