Drawing hour marks of a clock using OpenGL - c++

Question

here is my code:
void drawClock(void)
{
glClearColor(1.0,1.0,1.0,1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(0.0,0.0,0.0);
for(int i=0; i<12; i++){
glRotatef(30,0,0,1);
glTranslatef(5.2,0.0,0.0);
glutWireCube(2.0);
}
glFlush();
}
Here is my reshape function (without it I don't see anything, although I'm not sure how it really works)
void changeSize(int w, int h) {
// Prevent a divide by zero, when window is too short
// (you cant make a window of zero width).
if(h == 0) h = 1;
float ratio = 1.0* w / h;
// Reset the coordinate system before modifying
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// Set the viewport to be the entire window
glViewport(0, 0, w, h);
// Set the correct perspective.
gluPerspective(45,ratio,1,1000);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(0.0,0.0,70.0,
0.0,0.0,-1.0,
0.0f,1.0f,0.0f);
}
So I am trying to draw the hour marks of a clock using wire cubes of size 2.0, and each of these cubes must be 5.2 units away from the center. This is for an assignment, I know it is probably very simple but I just can't manage to make it work properly. My problem is that the cubes appear in 3D, but I want them to appear in 2D, as in I would only see one face. Also, the circle is not centered, I do not understand why. I know I am supposed to use pushMatrix and popMatrix but no matter how I use it it doesn't work.

Answer 1

3d Problem
gluPerspective makes a perspective projection. To accomplish what you need you should apply an orthographic projection instead.
The best way to do this with your current code is to us glOrtho to provide a left, right, bottom, top, far,near box within which everything will 'appear' 2D. Try the code below in place of gluPerspective.
glOrtho(10.0f,-10.0f,10.0f,-10.0f,10.0f,-10.0f,10.0f);
Position problem
I'm not so sure about the transformation as I've not used immediate mode for a while. Note the order of operations makes a difference.
As for the push/pop of matrices, it is basically a stack of 4x4 matrices detailing the transformations. I'm sure it works along the lines of
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslate(x,y,z);// Where x,y,z is the starting point of your clock
for(int i=0; i<12; i++){
glPushMatrix();
glRotatef(i * 30,0,0,1);
glTranslatef(5.2,0.0,0.0);
glutWireCube(2.0);
glPopMatrix();
}