Draw doesn't works with OpenGL while drawing sphere - c

Question

I'm first in OpenGL, and i want to draw a sphere with 3D graphical view.
For first step, i just want to draw a belt that contained to result sphere.
But there's no result, all of my result window is cleared with white.
Is there any problem in my code?
Here is my Code :
void init();
void display();
void drawPath(int pi, int theta);
void drawQuad(int pi, int theta);
int we = -80; // - 파이
int kyong = -180; // - 세타
int main(int argc, const char * argv[]) {
glutInit(&argc, (char**)argv);
glutInitWindowSize(500, 500);
glutCreateWindow("Prog09 - Goo");
glutDisplayFunc(display);
init();
glutMainLoop();
return 0;
}
void init(){
glClearColor(1, 1, 1, 1);
glOrtho(0, 50, 0, 50, -50, 50);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
}
void display(){
glColor3f(1.0, 1.0, 1.0);
drawPath(0, 0);
}
void drawPath(int pi, int theta){
drawQuad(pi, theta);
}
void drawQuad(pi, theta){
int i;
GLfloat x[4],y[4],z[4];
// theta = (theta * 3.14)/180;
// pi = (pi * 3.14)/180;
x[0] = sin(theta)*cos(pi);
y[0] = cos(theta)*sin(pi);
z[0] = sin(pi);
x[1] = sin(theta)*cos(pi+20);
y[1] = cos(theta)*sin(pi+20);
z[1] = sin(pi+20);
x[2] = sin(theta+20)*cos(pi+20);
y[2] = cos(theta+20)*sin(pi+20);
z[2] = sin(pi+20);
x[3] = sin(theta+20)*cos(pi);
y[3] = cos(theta+20)*sin(pi);
z[3] = sin(pi);
for (i = 0; i < 4; i++) {
glBegin(GL_POLYGON);
glVertex3f(x[i]*10, y[i]*10, z[i]*10);
glEnd();
}
glFlush();
for (i = 0; i < 4; i++) {
printf("%d. %f %f %f\n",i+1, x[i], y[i], z[i]);
}
printf("WHY?\n");
}
I know it's a basic question, but i have know idea why my codes doesn't work.
Thanks for your helps.

Answer 1

You are drawing a number of polygons, were each polygon contains exactly one point:
for (i = 0; i < 4; i++) {
glBegin(GL_POLYGON);
glVertex3f(x[i]*10, y[i]*10, z[i]*10);
glEnd();
}
If you want to draw one polygon with all the points, then you'll have to do something like:
glBegin(GL_POLYGON);
for (i = 0; i < 4; i++) {
glVertex3f(x[i]*10, y[i]*10, z[i]*10);
}
glEnd();