.OBJ groups and Unity

Question

I have an .OBJ file (which looks like this) and when I import the file into Unity (4.5.3f3) the second group (Square_Plane) does not import.

The .OBJ contains the following:

mtllib test.mtl
g Triangle_Plane.001
v -2.210575 0.000000 -0.986309
v -2.210575 0.000000 1.013691
v -4.210576 0.000000 1.013691
usemtl (null)
s off
f 1 3 2

g Square_Plane
v 1.000000 0.000000 -1.000000
v 1.000000 0.000000 1.000000
v -1.000000 0.000000 1.000000
v -1.000000 0.000000 -1.000000
usemtl (null)
s off
f 4 7 6 5

This is what it looks like outside of Unity: Then in Unity: Have I done something wrong in my .OBJ file, or does anyone know if there is an import setting or similar for Unity which will fix this issue?

Answer 1

Your file defines a quad. Unity doesn't like quads. If you split it up in two triangles it works:

mtllib test.mtl
g Triangle_Plane.001
v -2.210575 0.000000 -0.986309
v -2.210575 0.000000 1.013691
v -4.210576 0.000000 1.013691
usemtl (null)
s off
f 1 3 2

g Square_Plane
v 1.000000 0.000000 -1.000000
v 1.000000 0.000000 1.000000
v -1.000000 0.000000 1.000000
v -1.000000 0.000000 -1.000000
usemtl (null)
s off
f 4 7 6
f 4 6 5