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[CLI] meshopt compression breaks UV coordinates

See original GitHub issue

Describe the bug UV coordinates seem to break in some cases when applying meshopt compression.

To Reproduce Steps to reproduce the behavior:

Download the attached file MultipleUVRanges.zip
Run gltf-transform meshopt MultipleUVRanges.glb MultipleUVRanges.meshopt.glb
Open the file e.g. in https://sandbox.babylonjs.com/ (doesn’t load in gltf.report)
Note distorted UV coordinates on output file

Expected behavior Output file looks the same as input file chrome_ZiTdOLGFe9

Versions:

Version: 1.0.1
Environment: nodejs

Notes

doesn’t seem to happen when running gltfpack -c or -cc on the same file

Issue Analytics

State:
Created 2 years ago
Comments:9 (6 by maintainers)

Top GitHub Comments

3reactions

scurestcommented, Nov 28, 2021

(Talking about MultipleUVRanges.glb here.)

The problem is obviously that the TEXCOORD_0 acccessor is using buffer view 5, which has the wrong filter (OCTAHEDRAL, so it should be for normals).

Looking here

https://github.com/donmccurdy/glTF-Transform/blob/2b24c54e8c1631eda9f07c508ba15f413e81f45a/packages/extensions/src/ext-meshopt-compression/meshopt-compression.ts#L293

filter always stringifies as "[object Object]", so effectively the filter is missing from the key. My guess is that’s why the buffer views are colliding. The TEXCOORDs on the other quads don’t collide because they differ in the byteStride as well as the filter (since they don’t get quantized I guess).

Using filter.filter in the key fixes this case for me.

1reaction

donmccurdycommented, Dec 3, 2021

Thanks @hybridherbst! Confirmed that model is fixed as well – and just published the fix as v1.2.2.

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