My gluSphere is Missing Patches - opengl

Question

I'm trying to draw a sphere using gluSphere. The sphere appears but certain patches are missing whether I draw it as a filled polygons or a wire frame.
int width=800, height=600;
void myinit(void)
{
// set up overall light data, including specular=ambient=light colors
GLfloat light_position[]={ 10.0, 10.0, -10.0, 1.0 };
GLfloat light_color[]={ 1.0, 1.0, 1.0, 1.0 };
GLfloat ambient_color[]={ 0.0, 0.2, 0.2, 1.0 };
GLfloat mat_specular[]={ 1.0, 1.0, 1.0, 1.0 };
glClearColor( 0.0, 1.0, 1.0, 0.0 );
glShadeModel(GL_SMOOTH);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat_specular );
glLightfv(GL_LIGHT0, GL_POSITION, light_position );
glLightfv(GL_LIGHT0, GL_AMBIENT, ambient_color );
glLightfv(GL_LIGHT0, GL_SPECULAR, light_color );
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_color );
/* attributes */
glEnable(GL_LIGHTING); // so lighting models are used
glEnable(GL_LIGHT0); // we'll use LIGHT0
glEnable(GL_DEPTH_TEST); // allow z-buffer display
//glClearDepth(1);
}
void drawHead(){
GLUquadric *sphere=gluNewQuadric();
gluQuadricDrawStyle( sphere, GLU_FILL);
gluQuadricNormals( sphere, GLU_SMOOTH);
gluQuadricOrientation( sphere, GLU_OUTSIDE);
gluQuadricTexture( sphere, GL_TRUE);
//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glPushMatrix();
glTranslated(0,0,-5);
glRotated(30,1,1,1);
gluSphere(sphere,2.0,15,15);
glPopMatrix();
}
void display(){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1,1,0);
drawHead();
glutSwapBuffers();
}
void main(int argc, char** argv){
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(width,height);
glutInitWindowPosition(100,200);
glutCreateWindow("Automaton");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(90.0,1.0,0.0,20);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
myinit();
glutDisplayFunc(display);
glutMainLoop();
}

Answer 1

As per the docs, "...zNear must never be set to 0."
Bump your zNear out a bit, and your zFar a bit more:
gluPerspective( 90.0, 1.0, 1.0, 200.0 );
Complete:
#include <GL/glut.h>
int width=800, height=600;
void myinit(void)
{
// set up overall light data, including specular=ambient=light colors
GLfloat light_position[]={ 10.0, 10.0, -10.0, 1.0 };
GLfloat light_color[]={ 1.0, 1.0, 1.0, 1.0 };
GLfloat ambient_color[]={ 0.0, 0.2, 0.2, 1.0 };
GLfloat mat_specular[]={ 1.0, 1.0, 1.0, 1.0 };
glClearColor( 0.0, 1.0, 1.0, 0.0 );
glShadeModel(GL_SMOOTH);
glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, mat_specular );
glLightfv(GL_LIGHT0, GL_POSITION, light_position );
glLightfv(GL_LIGHT0, GL_AMBIENT, ambient_color );
glLightfv(GL_LIGHT0, GL_SPECULAR, light_color );
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_color );
/* attributes */
glEnable(GL_LIGHTING); // so lighting models are used
glEnable(GL_LIGHT0); // we'll use LIGHT0
glEnable(GL_DEPTH_TEST); // allow z-buffer display
}
void drawHead()
{
GLUquadric *sphere=gluNewQuadric();
gluQuadricDrawStyle( sphere, GLU_FILL);
gluQuadricNormals( sphere, GLU_SMOOTH);
gluQuadricOrientation( sphere, GLU_OUTSIDE);
gluQuadricTexture( sphere, GL_TRUE);
glPushMatrix();
glTranslated(0,0,-5);
glRotated(30,1,1,1);
gluSphere(sphere,2.0,15,15);
glPopMatrix();
}
void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor3f(1,1,0);
drawHead();
glutSwapBuffers();
}
void main(int argc, char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(width,height);
glutInitWindowPosition(100,200);
glutCreateWindow("Automaton");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective( 90.0, 1.0, 1.0, 200.0 );
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
myinit();
glutDisplayFunc(display);
glutMainLoop();
}