Lame OpenGL issue...

[atrx]

I'm rather confused on a somewhat basic openGL program, as there is a rather irritating bug. The program isn't much, just a simple, rotating cube with lighting, but the top and bottom of the cube have a blank triangle. I went through all the vertices to see if that one was misplaced, but I don't think that is the problem. Could be, but I don't know. Anyways, here's the code:

#include <iostream>
#include <stdlib.h>
#include <GL/glut.h>

using namespace std;

void handleKeypress(unsigned char key, int x, int y)
{
switch (key)
{
case 27:
exit(0);
}
}

void initRendering()
{
glEnable(GL_DEPTH_TEST);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_NORMALIZE);
glShadeModel(GL_SMOOTH);
}

void handleResize(int w, int h)
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0, (double)w / (double)h, 1.0, 200.0);
}

float angle;

void drawScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

//Lighting
GLfloat ambientColor[] = {0.3, 0.3, 0.3, 1.0};
glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambientColor);

GLfloat lightColor0[]= {1.0,1.0,1.0,1.0};
GLfloat lightPosition0[] = {-1.0,0.5,0.5,0.0};
glLightfv(GL_LIGHT0,GL_DIFFUSE,lightColor0);
glLightfv(GL_LIGHT0,GL_POSITION,lightPosition0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glPushMatrix();

glTranslatef(0.0,0.0,-5.0);
glRotatef(angle, 1.0, 0.0, 0.0);
glBegin(GL_QUADS);

glColor3f(0.5, 0.5, 0.0);

//Front
glNormal3f(0.0, 0.0, 1.0);
glVertex3f(-1.5, -1.0, 1.5);
glVertex3f(1.5, -1.0, 1.5);
glVertex3f(1.5, 1.0, 1.5);
glVertex3f(-1.5, 1.0, 1.5);

//Right
glNormal3f(1.0, 0.0, 0.0);
glVertex3f(1.5, -1.0, -1.5);
glVertex3f(1.5, 1.0, -1.5);
glVertex3f(1.5, 1.0, 1.5);
glVertex3f(1.5, -1.0, 1.5);

//Back
glNormal3f(0.0, 0.0, -1.0);
glVertex3f(-1.5, -1.0, -1.5);
glVertex3f(-1.5, 1.0, -1.5);
glVertex3f(1.5, 1.0, -1.5);
glVertex3f(1.5, -1.0, -1.5);

//Left
glNormal3f(-1.0, 0.0, 0.0);
glVertex3f(-1.5, -1.0, -1.5);
glVertex3f(-1.5, -1.0, 1.5);
glVertex3f(-1.5, 1.0, 1.5);
glVertex3f(-1.5, 1.0, -1.5);

//PROBLEM STARTS HERE (I think...)*******
//Top
glNormal3f(0.0,1.0,0.0);
glVertex3f(-1.5,1.0,1.5);
glVertex3f(1.5,1.0,1.5);
glVertex3f(-1.5,1.0,-1.5);
glVertex3f(1.5,1.0,-1.5);

//Bottom
glNormal3f(0.0,1.0,0.0);
glVertex3f(-1.5,-1.0,1.5);
glVertex3f(1.5,-1.0,1.5);
glVertex3f(-1.5,-1.0,-1.5);
glVertex3f(1.5,-1.0,-1.5);
//AND (MIGHT) END HERE********

glEnd();

glPopMatrix();
glutSwapBuffers();
}

void update(int value)
{
angle += 2.0;
if (angle >= 360)
angle = 0;

glutPostRedisplay();

glutTimerFunc(20, update, 0);
}

int main(int argc, char** argv)
{
//Initialize GLUT
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(1280, 800);

//Create the window
glutCreateWindow("OpenGL Test Window");
initRendering();

//Set handler functions
glutDisplayFunc(drawScene);
glutKeyboardFunc(handleKeypress);
glutReshapeFunc(handleResize);

glutTimerFunc(20, update, 0);

glutMainLoop();
return 0;
}

[GNU-Fan]

Looking at it casually, I see that the normal vectors are identical. Shouldn't they point in opposite directions?