无法正确定义一个QUAD

Question

I'm want to have a rectangular cube. One wall has face on the wrong side so I can't see pink colour. This is good side of the cube:

At the back of the cube there is grey back face of the wall:

This is the code:

glBegin(GL_QUADS);
    //floor
    glMaterialfv(GL_FRONT, GL_DIFFUSE, floor_diffuse);
    glVertex3f(-floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, 0, -floor_size_z / 2);

    //roof
    glMaterialfv(GL_FRONT, GL_DIFFUSE, roof_diffuse);
    glVertex3f(-floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, -floor_size_z / 2);      
    //walls
    glMaterialfv(GL_FRONT, GL_DIFFUSE, walls_diffuse);
    glVertex3f(-floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, 0, -floor_size_z / 2);

    glVertex3f(floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, -floor_size_z / 2);

    glVertex3f(-floor_size_x / 2, 0, -floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, -floor_size_z / 2);
    glVertex3f(floor_size_x / 2, 0, -floor_size_z / 2);     

    //BAD WALL
    glVertex3f(floor_size_x / 2, 0, floor_size_z / 2);
    glVertex3f(floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, wall_height, floor_size_z / 2);
    glVertex3f(-floor_size_x / 2, 0, floor_size_z / 2);

    glEnd();

I've tried all combinations (counter)clockwise order but result is still the same. Any ideas?

Answer 1

I believe you're identifying your walls incorrectly. The ones you create as 1st ( X = - floor_size_x / 2 ), 3rd ( Z = - floor_size_z / 2 ) and 4th ( Z = floor_size_z / 2 ) are all specified clockwise, while the 2nd one ( X = floor_size_x / 2 ) is specified counter-clockwise. I'd guess this is actually the incorrect one.