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jkuhlmann / cgltf

:diamond_shape_with_a_dot_inside: Single-file glTF 2.0 loader and writer written in C99
MIT License
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Meshes with more than 65535 verticies (that need 32-bit index buffer) not supported? #111

Closed EeroMutka closed 4 years ago

EeroMutka commented 4 years ago

When I load a mesh with more than 65535 verticies, cgltf discards all the extra verticies. The indices structs component_type stays at cgltf_component_type_r_16u and the position attribute structs count says 65535.

GLTF does support more than 65545 verticies, for example when I export and import back such a mesh in blender, it all works. Are you planning on making this work?

zeux commented 4 years ago

Do you have an example .gltf file? This works fine for me. component_type in particular is read from the .gltf componentType so if that uses a UNSIGNED_INT index type, you should get r_32u.

EeroMutka commented 4 years ago

Hmm, that's interesting. I don't see why it wouldn't work for me then. Here you go gltftest.zip

(in these images I actually loaded a .glb file, but the same thing happened with .gltf) image

image

zeux commented 4 years ago

Your glTF file doesn't use 32-bit indices. The mesh has 3 primitives, with 291552 indices & 65535 vertices in the first, 274953 indices & 61834 vertices in the second, and 213 indices & 89 vertices in the third one (you can see this by inspecting the gltf file, particularly the meshes and accessors used).

So cgltf correctly returns three primitives - it's up to your application to either decide to merge them or decide to keep them split and use 16-bit indices.

EeroMutka commented 4 years ago

Oh, I see. I guess the blender exporter splits it? I assumed that since I'm exporting only a single mesh container, it'd put it all in a single primitive. I should dig into the gltf spec more. Thanks for helping

Edit: yeah, the issue is with the blender gltf exporter. But its fixed in the latest version! Glad it was that easy. https://github.com/KhronosGroup/glTF-Blender-IO/issues/777