3d cube opengl - overlapping sides - c++

Question

I want to create a 3d cube with openGL. Also, I want to cover each side with an image that I transform in a texture.
I find cube coordinates in 2D, and I create a QUADS for each side.
My problem is that when I render textures corresponding cube sides, I see these textures overlap each other, as you can see in this image:
my code is:
Initialization:
glGenTextures(2, textures);
glClearColor (0.0, 0.0, 0.0, 0.0);
glClearDepth(1.0f); // Depth Buffer Setup
glEnable(GL_DEPTH_TEST); // Enables Depth Testing
glDepthFunc(GL_ALWAYS);
Transform image in thexture:
up = imread("up.png");
glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glBindTexture(GL_TEXTURE_2D, textures[1]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
gluBuild2DMipmaps(GL_TEXTURE_2D, GL_RGB, up.cols, up.rows, GL_RGB, GL_UNSIGNED_BYTE, up.data);
Display cube:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
// Set Projection Matrix
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, WIDTH, HEIGHT, 0);
// Switch to Model View Matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glBindTexture(GL_TEXTURE_2D, textures[1]);
glBegin(GL_QUADS);
//sopra
glTexCoord2f(0.0f, 0.0f); glVertex2f((GLfloat)((coord[6].x)),(GLfloat)(coord[6].y));
glTexCoord2f(1.0f, 0.0f); glVertex2f((GLfloat)((coord[5].x)),(GLfloat)(coord[5].y));
glTexCoord2f(1.0f, 1.0f); glVertex2f((GLfloat)((coord[4].x)),(GLfloat)(coord[4].y));
glTexCoord2f(0.0f, 1.0f); glVertex2f((GLfloat)((coord[7].x)),(GLfloat)(coord[7].y));
glEnd();
I do the same for the other sides of the cube.
The order in which I render textures is:
bottom (ground) side
up side
behind side
front side
left side
right side
what is wrong or what am I missing? Or, Maybe cannot create a 3d cube with 2d coordinates (glVertex2f (...))?
Thanks for your help!

Answer 1

You can't create a cube with 2d coordinates. The sides are overlapping because they are all on the same plane in space. A cube is in 3d space so needs 3 coordinates, x, y, and z.
So try using:
glVertex3f(x, y, z);
and use some appropriate z values depending on where you want each face.
For the texture you can still use:
glTexCoord2f(x, y);
since the textures are in 2 dimensional space.
If you are still confused about what to use for your coordinates I suggest you read this to help you understand 3d space in openGL:
http://www.falloutsoftware.com/tutorials/gl/gl0.htm