What is wrong with my quad .obj?

Questions & Answers
1

When importing the obj file below, unity says “Can’t import normals, because mesh ‘default’ doesn’t have it.”, and then unity recalculates the normals. So my first question is: why doesn’t unity parse my “vn” lines as vertex normals? The second issue is that the entire mesh is a solid color when I apply a texture image material, and I have tried a variety of shaders such as “Legacy Shaders/Diffuse”. So why doesn’t unity process my “vt” lines as texture coordinates and map an image onto this quad? This is a very simple object example of the issues I have with generating obj files from script. I have also tried adding in decimal places to these numbers. Please do not recommend any solutions involving 3d modeling programs.

v 0 0 0
v 100 0 0
v 0 0 100
v 100 0 100
vn 0 1 0
vn 0 1 0
vn 0 1 0
vn 0 1 0
vt 0 0
vt 1 0
vt 0 1
vt 1 1
f 1 4 3
f 1 2 4
2

Unity is parsing your normals, but your mesh is not using them.

In wavefront .obj file format a face can be defined in the following ways:

# vertex index
f 1 2 3
# vertex index / vertex texture coordinate index
f 1/1 2/2 3/3
# vertex index / vertex texture coordinate index / vertex normal index
f 1/1/1 2/2/2 3/3/3

Your .obj can be imported to unity if you change your face definitions as follows:

v 0 0 0
v 100 0 0
v 0 0 100
v 100 0 100
vn 0 1 0
vn 0 1 0
vn 0 1 0
vn 0 1 0
vt 0 0
vt 1 0
vt 0 1
vt 1 1
f 1/1/1 4/4/4 3/3/3
f 1/1/1 2/2/2 4/4/4