OpenGL Zoom In/Out on a Hexagon in an animation - opengl

Question

I'm trying to create an effect of zooming on a rotating hexagon. I'm accomplishing this by changing the window. Once it "zooms in" it supposed to "zoom out", and then repeat continuously. I've managed to zoom in just fine, and by the looks of my code, it should zoom out as well, but once it zooms in, nothing else is drawn. I've debugged my code, and i can tell that the variables are indeed being incremented on this line:
gluOrtho2D(cx - w, cx + w, cy -h, cy +h);
But yet i still fail to see my hexagon "zoom out". Any help would be appreciated. I'm pretty sure its something simple i'm forgetting. But it keeps eluding me. My code follows:
#include <cstdlib>
#include <GL/glut.h>
#include <cmath>
#define PI 3.14159265
#define ZOOM_IN 1
#define ZOOM_OUT -1
using namespace std;
const int screenWidth = 500;
const int screenHeight = 500;
float cx = 0.0, cy = 0.0; //center of viewport (cx, cy)
float h=1.2, w = 1.2; //window size
int NumFrames = 10; //frames
int frame = 0;
int direction = ZOOM_IN;
//<<<<<<<<<<<<<<<<<<<<<<< myInit >>>>>>>>>>>>>>>>>>>>
void myinit() {
glClearColor (1.0, 1.0, 1.0, 1.0); //set the background color to white
glColor3f (0.0, 0.0, 0.0); //set the foreground color to black
glPointSize (3.0); //set the point size to 3 X 3 pixels
glViewport (0.0, 0.0, 500.0, 500.0); //set the viewport to be the entire window
//set up a world window to screen transformation
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(-5.0, 5.0, -5.0, 5.0);
// glMatrixMode (GL_MODELVIEW);
}
//<<<<<<<<<<<<<<<<<<<<<<< hexswirl >>>>>>>>>>>>>>>>>>>>
void hexswirl() {
double angle; //the angle of rotation
double angleInc = 2*PI/6.0; //the angle increment
double inc = 5.0/50; //the radius increment
double radius = 5.0/50.0; //the radius to be used
//clear the background
glClear (GL_COLOR_BUFFER_BIT);
//draw the hexagon swirl
for (int j = 0; j <= 50; j++) {
//the angle of rotation depends on which hexagon is
//being drawn.
angle = j* (PI/180.0);
//draw one hexagon
glBegin (GL_LINE_STRIP);
for (int k=0; k <= 6; k++) {
angle += angleInc;
glVertex2d(radius * cos(angle), radius *sin(angle));
}
glEnd();
//determine the radius of the next hexagon
radius += inc;
}
//swap buffers for a smooth change from one
//frame to another
glutSwapBuffers();
glutPostRedisplay();
glFlush();
}
//<<<<<<<<<<<<<<<<<<<<<<< viewZoom >>>>>>>>>>>>>>>>>>>>
void viewZoom(int i) {
if(direction == ZOOM_IN) {
//change the width and height of the window each time
w *= 0.9;
h *= 0.9;
}
if(direction == ZOOM_OUT) {
w /= 0.9;
h /= 0.9;
}
if(i%10 == 0) {
direction = -direction;
}
//change the window and draw the hexagon swirl
gluOrtho2D (cx - w, cx + w, cy - h, cy + h);
hexswirl();
glutPostRedisplay();
glutTimerFunc(200, viewZoom,i+1);
}
//<<<<<<<<<<<<<<<<<<<<<<<< main >>>>>>>>>>>>>>>>>>>>>>
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize(screenWidth, screenHeight);
glutInitWindowPosition(100,100);
glutCreateWindow("hexanim");
glutDisplayFunc(hexswirl);
viewZoom(1);
myinit();
glutMainLoop();
return 1;
}

Answer 1

I figured out a way around my problem. I still don't know why my window wasn't redrawing after "zooming in", but i decided to implement it through changing my viewport instead. I ended up switching out:
gluOrtho2D (cx - w, cx + w, cy - h, cy + h);
for
cx = screenWidth / w;
cy = screenHeight / h;
glViewport((screenWidth-cx)/2, (screenHeight-cy)/2, cx, cy);
(and made all the corresponding changes associated with it).