zoom in and out

i have the view perspective like this

gluLookAt(5,5,10, -2,-2f-2, 0,1,0);

and i would like to make the up arrow key to zoom into the picture and make the down arrow key to zoom out the picture

any ideas how to do that?

thank you



float z = 10.0f; //declare as global variable

gluLookAt(5,5,z, -2,-2,-2, 0,1,0);

if (key_up)z–;
if (key_down)z++;

zoom and moving closer are two different things. for zoom you should change the FOV value of gluPespective