lack of extensions or so...

[tigrazone]

Hello! Thank you for fastgltf. It's impressive but not open all files from https://github.com/gkjohnson/3d-demo-data.git which use and can open https://github.com/gkjohnson/three-gpu-pathtracer.git For example, I try to open https://raw.githubusercontent.com/gkjohnson/3d-demo-data/main/models/pathtracing-bathroom/modernbathroom.glb and fastgltf_gl_viewer fails with error

Loading c:\msys64\home\user\from-git\3d-demo-data\models\pathtracing-bathroom\modernbathroom.glb
Failed to load glTF: One or more extensions are required by the glTF but not enabled in the Parser.
Failed to parse glTF.

I find here is extension list and extend it to all possible https://github.com/spnda/fastgltf/blob/d2e8a52bcf8b844570f9aee9a83c5341d1f476e4/examples/gl_viewer/gl_viewer.cpp#L289 with change to fastgltf::Parser parser((fastgltf::Extensions)~0);

After change fastgltf_gl_viewer fails with error

Loading c:\msys64\home\user\from-git\3d-demo-data\models\pathtracing-bathroom\modernbathroom.glb
Failed to load glTF: The glTF is either missing something or has invalid data.
Failed to parse glTF

Can you fix this error?

[spnda]

Hi, thanks for the report. First of all, the gl_viewer example simply does not support the EXT_meshopt_compression. I want to keep the example at a bare minimum and only support the core glTF specification. While some extensions are widely used, I will not add code to support them to the example. KHR_mesh_quantization was the only one I added because it required no additional code.

As for the parsing error you experienced after enabling the extensions in the parser, it turns out there was a part of the spec for EXT_meshopt_compression that I seem to have missed. It adds the concept of so-called fallback buffers which are buffers with a byteLength property but they contain no data. The code currently throws an error in this case because it expects to either have a uri property or use the GLB buffer, which is why you're getting that error.

I've now changed the code in an upcoming commit that adds a new (empty) data source called ´Fallback` that is used whenever the library detects the extension is enabled (and required by the asset) and a buffer has no data. It is then the users responsibility to always use the compressed buffer version.