How to draw this object with OpenGL - opengl

Question

I am trying to draw something like this in OpenGL 2.1 using GLU and GLUT primitives such as gluCylinder, glutSolidCylinder, etc.
Basically it's a solid cylinder with a hole in the middle. So far I was unable to achieved it.
I also tried to import wavefront obj from Blender to my program in C++ but what I got was this.
glBegin(GL_TRIANGLES);
for(int i = 0; i < wheel->faces.size(); i++) {
int nx = atoi(wheel->faces.at(i).at(0).substr(wheel->faces.at(i).at(0).find_last_of('/') + 1).c_str()) - 1;
int ny = atoi(wheel->faces.at(i).at(1).substr(wheel->faces.at(i).at(1).find_last_of('/') + 1).c_str()) - 1;
int nz = atoi(wheel->faces.at(i).at(2).substr(wheel->faces.at(i).at(2).find_last_of('/') + 1).c_str()) - 1;
int vx = atoi(wheel->faces.at(i).at(0).substr(0, wheel->faces.at(i).at(0).find_first_of('/')).c_str()) - 1;
int vy = atoi(wheel->faces.at(i).at(1).substr(0, wheel->faces.at(i).at(1).find_first_of('/')).c_str()) - 1;
int vz = atoi(wheel->faces.at(i).at(2).substr(0, wheel->faces.at(i).at(2).find_first_of('/')).c_str()) - 1;
glNormal3f(wheel->normals.at(nx).x, wheel->normals.at(ny).y, wheel->normals.at(nz).z);
glVertex3f(wheel->vertices.at(vx).x, wheel->vertices.at(vy).y, wheel->vertices.at(vz).z);
}
glEnd();
The parsing should be correct, I double checked it line by line. I guess it's the wrong way I tried to draw it.
However I don't want to use obj since my way of drawing makes animation slow (I am fairly new to OpenGL). And I don't want to use OpenGL 3+ either.
Any suggestions?

Answer 1

In your code you're drawing a single point with one face, however a face (a triangle) here is supposed to have three points.
Your may try this code:
glBegin(GL_TRIANGLES);
for(int i = 0; i < wheel->faces.size(); i++) {
int v0 = atoi(wheel->faces.at(i).at(0).substr(0, wheel->faces.at(i).at(0).find_first_of('/')).c_str()) - 1;
int v1 = atoi(wheel->faces.at(i).at(1).substr(0, wheel->faces.at(i).at(1).find_first_of('/')).c_str()) - 1;
int v2 = atoi(wheel->faces.at(i).at(2).substr(0, wheel->faces.at(i).at(2).find_first_of('/')).c_str()) - 1;
glVertex3f(wheel->vertices.at(v0).x, wheel->vertices.at(v0).y, wheel->vertices.at(v0).z);
glVertex3f(wheel->vertices.at(v1).x, wheel->vertices.at(v1).y, wheel->vertices.at(v1).z);
glVertex3f(wheel->vertices.at(v2).x, wheel->vertices.at(v2).y, wheel->vertices.at(v2).z);
}
glEnd();
I removed the normal part since I don't think you would need it for now. You may add it later.
EDTIED:
This seems better:
glBegin(GL_TRIANGLES);
for(int i = 0; i < wheel->faces.size(); i++)
for (int j = 0; j < 3; j++)
{
int v_id = atoi(wheel->faces.at(i).at(j).substr(0, wheel->faces.at(i).at(j).find_first_of('/')).c_str()) - 1;
glVertex3f(wheel->vertices.at(v_id).x, wheel->vertices.at(v_id).y, wheel->vertices.at(v_id).z);
}
glEnd();

Answer 2

Found for my self this small lib for opening obj files.
Drawing loaded mesh with next code:
glBegin(GL_TRIANGLES);
for (size_t f = 0; f < shapes[0].mesh.indices.size(); f++) {
glVertex3f(shapes[0].mesh.positions[3*f+0],
shapes[0].mesh.positions[3*f+1],
shapes[0].mesh.positions[3*f+2]);
}
glEnd();
Load mesh:
std::vector<tinyobj::shape_t> shapes;
int loadMesh(const char *file) {
const char* basepath = NULL;
std::string err = tinyobj::LoadObj(shapes, file, basepath);
if (!err.empty()) {
std::cerr << err << std::endl;
return 0;
}
std::cout << "# of shapes : " << shapes.size() << std::endl;
return 1;
}