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/* sphere, Copyright (c) 2002 Paul Bourke <pbourke@swin.edu.au>,
* Copyright (c) 2010-2014 Jamie Zawinski <jwz@jwz.org>
* Utility function to create a unit sphere in GL.
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation. No representations are made about the suitability of this
* software for any purpose. It is provided "as is" without express or
* implied warranty.
*
* 8-Oct-98: dek Released initial version of "glplanet"
* 21-Mar-01: jwz@jwz.org Broke sphere routine out into its own file.
* 28-Feb-02: jwz@jwz.org New implementation from Paul Bourke:
* http://astronomy.swin.edu.au/~pbourke/opengl/sphere/
* 21-Aug-10 jwz@jwz.org Converted to use glDrawArrays, for OpenGL ES.
*/
#include <math.h>
#include <stdlib.h>
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#ifdef HAVE_COCOA
#elif defined(HAVE_ANDROID)
# include <GLES/gl.h>
#else /* real X11 */
# include <GL/gl.h>
#endif
#ifdef HAVE_JWZGLES
# include "jwzgles.h"
#endif /* HAVE_JWZGLES */
#include "sphere.h"
typedef struct { GLfloat x, y, z; } XYZ;
static int
unit_sphere_1 (int stacks, int slices, int wire_p, int half_p)
{
int polys = 0;
int i,j;
double theta1, theta2, theta3;
XYZ p, n;
XYZ la = { 0, -1, 0 }, lb = { 0, -1, 0 };
XYZ c = {0, 0, 0}; /* center */
double r = 1.0; /* radius */
int stacks2 = stacks * 2;
int end = (half_p ? stacks/2 : stacks);
int mode = (wire_p ? GL_LINE_STRIP : GL_TRIANGLE_STRIP);
int arraysize, out;
struct { XYZ p; XYZ n; GLfloat s, t; } *array;
if (r < 0)
r = -r;
if (slices < 0)
slices = -slices;
arraysize = (stacks+1) * (slices+1) * (wire_p ? 4 : 2);
array = (void *) calloc (arraysize, sizeof(*array));
if (! array) abort();
out = 0;
if (slices < 4 || stacks < 2 || r <= 0)
{
mode = GL_POINTS;
array[out++].p = c;
goto END;
}
for (j = 0; j < end; j++)
{
theta1 = j * (M_PI+M_PI) / stacks2 - M_PI_2;
theta2 = (j + 1) * (M_PI+M_PI) / stacks2 - M_PI_2;
for (i = slices; i >= 0; i--)
{
theta3 = i * (M_PI+M_PI) / slices;
if (wire_p)
{
array[out++].p = lb; /* vertex */
array[out++].p = la; /* vertex */
}
n.x = cos (theta2) * cos(theta3);
n.y = sin (theta2);
n.z = cos (theta2) * sin(theta3);
p.x = c.x + r * n.x;
p.y = c.y + r * n.y;
p.z = c.z + r * n.z;
array[out].p = p; /* vertex */
array[out].n = n; /* normal */
array[out].s = i / (GLfloat) slices; /* texture */
array[out].t = 2*(j+1) / (GLfloat) stacks2;
out++;
if (wire_p) la = p;
n.x = cos(theta1) * cos(theta3);
n.y = sin(theta1);
n.z = cos(theta1) * sin(theta3);
p.x = c.x + r * n.x;
p.y = c.y + r * n.y;
p.z = c.z + r * n.z;
array[out].p = p; /* vertex */
array[out].n = n; /* normal */
array[out].s = i / (GLfloat) slices; /* texture */
array[out].t = 2*j / (GLfloat) stacks2;
out++;
if (out >= arraysize) abort();
if (wire_p) lb = p;
polys++;
}
}
END:
glEnableClientState (GL_VERTEX_ARRAY);
glEnableClientState (GL_NORMAL_ARRAY);
glEnableClientState (GL_TEXTURE_COORD_ARRAY);
glVertexPointer (3, GL_FLOAT, sizeof(*array), &array[0].p);
glNormalPointer ( GL_FLOAT, sizeof(*array), &array[0].n);
glTexCoordPointer (2, GL_FLOAT, sizeof(*array), &array[0].s);
glDrawArrays (mode, 0, out);
free (array);
return polys;
}
int
unit_sphere (int stacks, int slices, int wire_p)
{
return unit_sphere_1 (stacks, slices, wire_p, 0);
}
int
unit_dome (int stacks, int slices, int wire_p)
{
return unit_sphere_1 (stacks, slices, wire_p, 1);
}
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