IMPORTOBJ only computed face normals when the file listed no normals at
all. When a file did list some, a face that omitted its normal indices,
or pointed at an index past the end of the list, kept a zero normal. That
zero reaches the mesh shader, which normalizes it for lighting.
Track which vertices got a normal from the file and give the rest their
face normal. Supplied normals are kept, and a file without normals is
handled as before.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
