Real-Time 3D Graphics with WebGL 2 - Second Edition

Vertex//Normal

There can also be cases where normals are defined but texture coordinates are not. In this case, the second part of the face configuration is missing:

f i1//n1 i2//n2 i3//n3...

This is the case for square.obj, which looks like this:

f 6//1 4//1 3//1f 6//1 3//1 5//1

Note that faces are defined using indices. In our example, we have defined a square divided into two parts. Here, we can see that all of the vertices share the same normal, which has been identified with index 1.

The remaining lines in this file represent the red group:

g squares_mesh_redusemtl redf 1//1 6//1 5//1f 1//1 5//1 2//1

As we mentioned previously, groups belonging to the same object share indices.