OBJ Model format

For most of time we are using WaveFront OBJ 3D Model format.

A basic OBJ file is composed of the vertex data and face data.

Vertex data includes vertex position list and optional lists such as vertex normal list, texture coordinate list.

Face data uses vertex indices and attribute indices to describe each face vertex.

We only deal with triangle meshes.

An example OBJ file of a unit cube is as follows. But we only support those OBJ files whose texture list and normal list are as long as the vertex list.

In this lab we don't need texture coordinates.

# vertex list
v 1.000000 -1.000000 -1.000000
v 1.000000 -1.000000 1.000000
v -1.000000 -1.000000 1.000000
v -1.000000 -1.000000 -1.000000
v 1.000000 1.000000 -0.999999
v 0.999999 1.000000 1.000001
v -1.000000 1.000000 1.000000
v -1.000000 1.000000 -1.000000

# texture list
vt 1.000000 0.333333
vt 1.000000 0.666667
vt 0.666667 0.666667
vt 0.666667 0.333333
vt 0.666667 0.000000
vt 0.000000 0.333333
vt 0.000000 0.000000
vt 0.333333 0.000000
vt 0.333333 1.000000
vt 0.000000 1.000000
vt 0.000000 0.666667
vt 0.333333 0.333333
vt 0.333333 0.666667
vt 1.000000 0.000000

# normal list
vn 0.000000 -1.000000 0.000000
vn 0.000000 1.000000 0.000000
vn 1.000000 0.000000 0.000000
vn -0.000000 0.000000 1.000000
vn -1.000000 -0.000000 -0.000000
vn 0.000000 0.000000 -1.000000

# face data with indices of v/vt/vn
f 2/1/1 3/2/1 4/3/1
f 8/1/2 7/4/2 6/5/2
f 5/6/3 6/7/3 2/8/3
f 6/8/4 7/5/4 3/4/4
f 3/9/5 7/10/5 8/11/5
f 1/12/6 4/13/6 8/11/6
f 1/4/1 2/1/1 4/3/1
f 5/14/2 8/1/2 6/5/2
f 1/12/3 5/6/3 2/8/3
f 2/12/4 6/8/4 3/4/4
f 4/13/5 3/9/5 8/11/5
f 5/6/6 1/12/6 8/11/6