Exporting gltf with draco compression messes up the vertex color

[jespertheend]

Describe the bug
When exporting a mesh with vertex colors as glb with draco compression enabled. The exported vertex color is different from what it should be. I haven't been able to import the exported glb into blender to check if this is a bug with blender or if it's an issue with three.js. But my exported mesh fails to render correctly both in https://threejs.org/editor/ as well as on https://gltf-viewer.donmccurdy.com/ and on https://sandbox.babylonjs.com/

To Reproduce
-Create a simple mesh with vertex colors (see attached blend file)
-Export as glb
-Export again as glb but with draco mesh compression enabled
-Notice how vertexColorTest.glb works fine on the websites mentioned above, but how vertexColorTestCompressed.glb doesn't.

Screenshots

no compression (left) vs draco compression (right)

.blend file/ .gltf
vertexColorTest.zip

Version
Operating system: Darwin-19.4.0-x86_64-i386-64bit 64 Bits
version: 2.83 (sub 13), branch: master, commit date: 2020-04-08 21:23, hash: rB1239cab11ff9

Additional context
https://gltf.insimo.com/ has an implementation of draco mesh compression with working vertex colors. Notice how 'vertexColorTest insimo.glb' works on all sites mentioned above.

[julienduroure]

@McNopper Can you please assign to someone of your team?

[BenCidPerez]

Any news on this? The bug persists and makes using the exporter's draco compression unusable for all projects that rely on the vertex color data to be accurate.

[jespertheend]

In case it helps anyone, for the time being we ended up using https://github.com/CesiumGS/gltf-pipeline to compress all our assets in bulk.

[ghost]

With the PR #1268, the compressed models are properly exported, though not all viewers display it correctly, such as Babylon (https://sandbox.babylonjs.com). Don McCurdy's viewer (https://gltf-viewer.donmccurdy.com) for instance does it right.

[jespertheend]

Thanks! Looking forward to this :)