triangulate faces obj format problem

Question

This is probably a noob question but here goes. I don't remember how to export correctly to my own obj parser.

this is how I want the faces to be exported (How they used to be exported correctly):

f 5/1/1 6/2/1 1/3/1
f 6/1/2 7/2/2 3/4/2
f 7/1/3 8/2/3 4/4/3
f 8/1/4 5/2/4 1/4/4
f 1/1/5 2/2/5 3/4/5
f 8/1/6 7/2/6 6/4/6
f 6/2/1 2/4/1 1/3/1
f 2/3/2 6/1/2 3/4/2
f 3/3/3 7/1/3 4/4/3
f 4/3/4 8/1/4 1/4/4
f 4/3/5 1/1/5 3/4/5
f 5/3/6 8/1/6 6/4/6

But everything I try with the exporter now only gives me something like this:

f 5//1 6//1 1//1
f 6//2 7//2 3//2
f 7//3 8//3 4//3
f 8//4 5//4 1//4
f 1//5 2//5 3//5
f 8//6 7//6 6//6
f 6//1 2//1 1//1
f 2//2 6//2 3//2
f 3//3 7//3 4//3
f 4//4 8//4 1//4
f 4//5 1//5 3//5
f 5//6 8//6 6//6

What am I doing wrong? I have tried converting all quads in edit mode to triangles manually in vain, and tested all export variables. I've tried different versions of blender too.

Answer 1

In the Wavefront file-format, the second number for every element for a face is the texture-coordinate

The quick way to get it running: Select your object, go into edit-mode, press U and select Unwrap.

When exporting, make sure you have Include UVs selected.

Outcome (only faces):

f 2/1/1 3/2/1 4/3/1
f 8/1/2 7/2/2 6/3/2
f 5/1/3 6/2/3 2/3/3
f 6/1/4 7/2/4 3/3/4
f 3/4/5 7/1/5 8/2/5
f 1/1/6 4/2/6 8/3/6
f 1/4/1 2/1/1 4/3/1
f 5/4/2 8/1/2 6/3/2
f 1/4/3 5/1/3 2/3/3
f 2/4/4 6/1/4 3/3/4
f 4/3/5 3/4/5 8/2/5
f 5/4/6 1/1/6 8/3/6