#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>

#define	PI 3.141592654

void DibujarEjes(void)
{
 glBegin(GL_LINES);
 //eje X
 glVertex3f(-1.5, 0.0, 0.0);
 glVertex3f(1.5, 0.0, 0.0);
 //eje Y
 glVertex3f(0.0, -1.5, 0.0);
 glVertex3f(0.0, 1.5, 0.0);
 //eje Z
 glVertex3f(0.0, 0.0, -1.5);
 glVertex3f(0.0, 0.0, 1.5);
 glEnd();
}

void DibujarEsfera(void)
{
 float x, y, z;
 float r=1.0, rho, theta;
 int i, j;

 glBegin(GL_POINTS);
 rho=0.0;
 x=(float)(r*sin(rho)*cos(theta));
 y=(float)(r*sin(rho)*sin(theta));
 z=(float)(r*cos(rho));
 glVertex3f(x, y, z);
 for (i=1; i<23; i++) {
	rho=PI*i/24;
	for (j=0; j<16; j++) {
		theta=2*PI*j/16;
		x=(float)(r*sin(rho)*cos(theta));
		y=(float)(r*sin(rho)*sin(theta));
		z=(float)(r*cos(rho));
		glVertex3f(x, y, z);
		}
	}
 rho=PI;
 x=(float)(r*sin(rho)*cos(theta));
 y=(float)(r*sin(rho)*sin(theta));
 z=(float)(r*cos(rho));
 glVertex3f(x, y, z);
 glEnd();
}

void init(void)
{
 glClearColor(0.0, 0.0, 0.0, 0.0);
}

void display(void)
{
 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 glPushMatrix();
 gluLookAt(2.0, 2.0, 4.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
 //ejes en verde
 glColor3f (0.0, 1.0, 0.0);  
 DibujarEjes();
 //ejes en amarillo
 glColor3f (1.0, 1.0, 0.0);  
 DibujarEsfera();
 glPopMatrix();
 glFlush();
}

void reshape(int w, int h)
{
 if (!h)
	return;
 glViewport(0, 0,  (GLsizei) w, (GLsizei) h);
 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
 gluPerspective(45.0, (GLfloat) w/(GLfloat) h, 1.0, 100.0);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
}

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

int main(int argc, char **argv)
{
 glutInit(&argc, argv);
 glutInitWindowSize(400, 400);
 glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
 glutCreateWindow("Coordenadas Esfericas");
 init();
 glutDisplayFunc(display);
 glutReshapeFunc(reshape);
 glutKeyboardFunc(keyboard);
 glutMainLoop();
 return 0;
}