Export to GLB: weird vertices count

Support Animation and Rigging
1

Hi,

when exporting a model from FBX to GLB, the POSITION attribute has a differing count depending on one option: UVs.

If unchecked, the vertices count is correct. When checked, it adds a number of vertices to the POSITION attribute and I don’t know what rule is applied here. I expected the count to go to TEXCOORD_x not merged with Position.

What is the rule here?

Thanks

2

Haven’t tested, don’t even know what GLB is, but I’d suspect it’s splitting vertices along UV seams. This is pretty typical for engines that don’t support per-face vertex data (you’d also see splitting for per-face normals, like sharp edges, as well.)

3

Aaah, that’s interesting, I will investigate, thanks a lot for the pointer!

4

@bandages is correct – glTF stores vertex data in the format expected by GPUs for faster loading / viewing in engines. This requires splitting shared per-face normals and UVs, with per-face normals generally increasing vertex counts more. If your model happens to use only per-face normals, you can just uncheck Geometry → Normals at export. If normals aren’t exported they won’t split vertices, and glTF viewers will infer flat normals.

5

Hi Don,

Thanks for the input (that I missed for some reason :cry:)!