OpenGL draw sphere using glVertex3f

Question

I needed to draw sphere on OpenGL without using gluSphere() function. I have found somewhere this function:

    void drawSphere(double r, int lats, int longs) {
    int i, j;
    for(i = 0; i <= lats; i++) {
        double lat0 = M_PI * (-0.5 + (double) (i - 1) / lats);
       double z0  = sin(lat0);
       double zr0 =  cos(lat0);

       double lat1 = M_PI * (-0.5 + (double) i / lats);
       double z1 = sin(lat1);
       double zr1 = cos(lat1);

       glBegin(GL_QUAD_STRIP);
       for(j = 0; j <= longs; j++) {
           double lng = 2 * M_PI * (double) (j - 1) / longs;
           double x = cos(lng);
           double y = sin(lng);

           glNormal3f(x * zr0, y * zr0, z0);
           glVertex3f(x * zr0, y * zr0, z0);
           glNormal3f(x * zr1, y * zr1, z1);
           glVertex3f(x * zr1, y * zr1, z1);
       }
       glEnd();
   }
 }

But I can't understand what it does. I think it draws polyhedron that looks like sphere. Also, I think lat0, lat1 used to determine how far from Z axis vertices will be located.

Your understanding is mostly correct. Have you ever worked with polar coordinates? This is similar. You can think of latitudes as slices through the sphere, just like on a globe of the earth. For a given latitude, you would need to generate points all around the circle at that latitude. That's what you're seeing with the sines and cosines. — user1118321, Feb 27 '14 at 06:12
http://stackoverflow.com/questions/7687148/drawing-sphere-in-opengl-without-using-glusphere — Toby Hodges, Jun 28 '16 at 21:47

OpenGL draw sphere using glVertex3f

0 Answers0