nil exception in gltf loader about tetra3d HOT 2 OPEN

Note I'm making some hand crafted gltf files that are likely straight up broken, e.g., I added

newMat.BackfaceCulling = !gltfMat.DoubleSided
		fmt.Printf("%+v\n", gltfMat)

and it dumps:
&{Extensions:map[] Extras: Name:rstb PBRMetallicRoughness: NormalTexture: OcclusionTexture: EmissiveTexture: EmissiveFactor:[0 0 0] AlphaMode:0 AlphaCutoff:0xc0002b8888 DoubleSided:false}

You can see I'm not setting PBRMetallicRoughness and line 158 of gltf.go is assuming this is always set and never nil, a simple nil check will make this more elegantly fail in future

from tetra3d.

Thanks for the report; I'll look into this, but it'll understandably be low-priority as hand-crafted / broken GLTF files should be fixed before use, and Tetra3D is primarily made to render things exported with Tetra3D from Blender (though you can use it with other files as well).

from tetra3d.