//Sphere Approximation Example
//Derived from E. Angel
//Alan Jamieson
//COSC 338 - Spring 2008

#include <GLUT/glut.h>
#include <math.h>

#define M_PI 3.14159265

void myinit(void){

	glClearColor(0.0, 0.0, 0.0, 0.0);
	glColor3f(0.0, 1.0, 0.0);
	
	glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

//	glPolygonMode(GL_FRONT, GL_LINE);
//	glPolygonMode(GL_BACK, GL_FILL);

//	glPolygonMode(GL_FRONT_AND_BACK, GL_POINT);

}

void display(void){
	
	float c = M_PI/180.0;
	float phi, theta, phir, phir20, thetar, x, y, z, c80;
	
	glClear(GL_COLOR_BUFFER_BIT);
	
	for (phi = -80.0; phi <= 80.0; phi += 5.0){
		phir = c*phi;
		phir20 = c*(phi+5);
		glBegin(GL_QUAD_STRIP);
		for (theta = -180.0; theta <= 180.0; theta += 5.0){
			thetar = c*theta;
			x = sin(thetar)*cos(phir);
			y = cos(thetar)*cos(phir);
			z = sin(phir);
			glVertex3d(x,y,z);
			x = sin(thetar)*cos(phir20);
			y = cos(thetar)*cos(phir20);
			z = sin(phir20);
			glVertex3d(x,y,z);
		}
		glEnd();
	
	}
	
	glBegin(GL_TRIANGLE_FAN);
		glVertex3d(0.0, 0.0, 1.0);
		c80 = c*80.0;
		z = sin(c80);
		for (theta = -180.0; theta <= 180.0; theta += 5.0){
			thetar = c *theta;
			x = sin(thetar)*cos(c80);
			y = cos(thetar)*cos(c80);
			glVertex3d(x, y, z);
		}
	glEnd();
	
	glBegin(GL_TRIANGLE_FAN);
		glVertex3d(0.0, 0.0, -1.0);
		z = -sin(c80);
		for (theta = -180.0; theta <= 180.0; theta += 20.0){
			thetar = c*theta;
			x=sin(thetar)*cos(c80);
			y=cos(thetar)*cos(c80);
			glVertex3d(x,y,z);
		}
	glEnd();

	glFlush();
}

void main(int argc, char** argv){

	glutInit(&argc, argv);
	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize(500,500);
	glutInitWindowPosition(0,0);
	glutCreateWindow("Sphere Approximation");
	glutDisplayFunc(display);
	
	myinit();
	
	glutMainLoop();
}