beginner wants to zoom

Hi all
i have drawn a graph. i want zoom functionality on the mouse click. any hints/clues/sample apps would be greatly appreciated.

make the graph bigger.
using a perspective projection u can use a smaller FOV.
with an orthogonal projection use glScale.(…)

Youre speaking greek…Im too new at this. What is FOV and please explain how making the graph bigger accomplishes my goal?

void ChangeSize(GLsizei w, GLsizei h)
{
if(h==0)
h=1;
glViewport(0,0,w,h);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();

GLfloat aspect=(GLfloat(w)/GLfloat(h));

gluPerspective(15.0, aspect, 0.01, 500.0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

}

the value 25.0 in the gluPerspective(); is the field of view. if it shrinks then the scene looks like it zooms in.

[This message has been edited by grady (edited 01-08-2001).]

Thanx…works like a charm