BabylonJS Renders GLTF Incorrectly, Some Faces Are Wrong Way

[apptaro]

I have some GLTF files which BabylonJS renders incorrectly; some faces are in wrong direction.

Cesium renders correctly, Three.js renders incorrectly as the same as BabylonJS.

GLTF files are converted from DAE with COLLADA2GLTF 2.1.2 for Win64. I have attached the zip containing .dae and .gltf.

I wonder if it's a bug of BabylonJS, or a bug of COLLADA2GLTF.

data.zip

[Guest]

Hello can you try to validate the file with http://github.khronos.org/glTF-Validator/ ?

Pinging @bghgary

[bghgary]

Looks like the left arm asset has a negative scale on it which according to spec is supposed to flip the triangles. Looks like Cesium doesn't handle this properly. You can test this using asset 01 from the negative scale tests from the asset generator project. I'll send a note to Cesium to let them know about this.

I think the source DAE model is wrong. If I import the left-arm.dae into Unity, the same thing happens where all the triangles are flipped.

[apptaro]

8 hours ago, Deltakosh said:

Hello can you try to validate the file with http://github.khronos.org/glTF-Validator/ ?

Pinging @bghgary

@Deltakosh The validator says "The asset is valid."

[apptaro]

9 hours ago, bghgary said:

Looks like the left arm asset has a negative scale on it which according to spec is supposed to flip the triangles. Looks like Cesium doesn't handle this properly. You can test this using asset 01 from the negative scale tests from the asset generator project. I'll send a note to Cesium to let them know about this.

I think the source DAE model is wrong. If I import the left-arm.dae into Unity, the same thing happens where all the triangles are flipped.

@bghgary You are right. I imported the left arm .dae to Blender and I found that the triangles are flipped. The .dae file, Cesium and my dae viewer based on papervision3d were the wrong ones.