gluLookAt causes blank screen [closed]

Question

I'm doing a C++ exercise for university. Basically it's supposed to be a golfball going into a hole. I've tried to implement the gluLookAt function but it produces a blank screen and I have no idea what I'm doing wrong. I'm guessing I'm not using it properly with Projection mode. Any help would be very much appreciated. Thanks.

code here: http://pastebin.com/RqTxNf9U

Answer 1

You are not pointing the camera at the ball. You are looking at {0, 0, 10} but the ball's initial position is at {0, 0.4, 0.8}. Change the lookat point (param 4-6) to something like {0, 0, 0}, so you are looking near the ball, i.e:

gluLookAt(
    // eye position:     
    0.0, 2.0, -3.0, 
    // look at point (this was wrong)
    0.0, 0.0, 0.0, 
    // up-vector
    0.0, 1.0, 0.0);

or even better, use the ball's position directly for the lookat point, this will move the camera each frame to point to the ball:

gluLookAt(
    // eye position:     
    0.0, 2.0, -3.0, 
    // look at point, look at the ball each frame
    golfball.getpx(), golfball.getpy(), golfball.getpz(), 
    // up-vector
    0.0, 1.0, 0.0);

But for this to work, you have to fix the rendering of the ball's position, remove startdispzotherwise you are not redering the ball on the correct position, change it to:

    glTranslatef(golfball.getpx(),golfball.getpy(), golfball.getpz());
    glutSolidSphere(golfball.getballsize(),20,20);

Answer 2

You're telling gluLookAt to look up into the sky. Check the documentation.

Your screen will be slightly less blank if you look at the ball. Or alternately, almost anywhere that isn't ten meters up in the air, precisely away from where the interesting stuff in the scene might be.