http://packetstormsecurity.org/UNIX/admin/xscreensaver-3.31.tar.gz

[xscreensaver] / hacks / glx / sphere.c

diff --git a/hacks/glx/sphere.c b/hacks/glx/sphere.c
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+/* sphere, Copyright (c) 1998 David Konerding <dek@cgl.ucsf.edu>
+ * 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.
+ */
+
+#include "config.h"
+#include <stdlib.h>
+#include <math.h>
+#include <GL/glx.h>
+#include "tube.h"
+
+/* Function for determining points on the surface of the sphere */
+static void
+parametric_sphere (float theta, float rho, GLfloat *vector)
+{
+  vector[0] = -sin(theta) * sin(rho);
+  vector[1] = cos(theta) * sin(rho);
+  vector[2] = cos(rho);
+}
+
+
+void
+unit_sphere (int stacks, int slices, Bool wire)
+{
+  int i, j;
+  float drho, dtheta;
+  float rho, theta;
+  GLfloat vector[3];
+  GLfloat ds, dt, t, s;
+
+  if (!wire)
+    glShadeModel(GL_SMOOTH);
+
+  /* Generate a sphere with quadrilaterals.
+   * Quad vertices are determined using a parametric sphere function.
+   * For fun, you could generate practically any parameteric surface and
+   * map an image onto it. 
+   */
+  drho = M_PI / stacks;
+  dtheta = 2.0 * M_PI / slices;
+  ds = 1.0 / slices;
+  dt = 1.0 / stacks;
+
+  glFrontFace(GL_CCW);
+  glBegin (wire ? GL_LINE_LOOP : GL_QUADS);
+
+  t = 0.0;
+  for (i=0; i < stacks; i++) {
+    rho = i * drho;
+    s = 0.0;
+    for (j=0; j < slices; j++) {
+      theta = j * dtheta;
+
+      glTexCoord2f (s,t);
+      parametric_sphere (theta, rho, vector);
+      glNormal3fv (vector);
+      parametric_sphere (theta, rho, vector);
+      glVertex3f (vector[0], vector[1], vector[2]);
+
+      glTexCoord2f (s,t+dt);
+      parametric_sphere (theta, rho+drho, vector);
+      glNormal3fv (vector);
+      parametric_sphere (theta, rho+drho, vector);
+      glVertex3f (vector[0], vector[1], vector[2]);
+
+      glTexCoord2f (s+ds,t+dt);
+      parametric_sphere (theta + dtheta, rho+drho, vector);
+      glNormal3fv (vector);
+      parametric_sphere (theta + dtheta, rho+drho, vector);
+      glVertex3f (vector[0], vector[1], vector[2]);
+
+      glTexCoord2f (s+ds, t);
+      parametric_sphere (theta + dtheta, rho, vector);
+      glNormal3fv (vector);
+      parametric_sphere (theta + dtheta, rho, vector);
+      glVertex3f (vector[0], vector[1], vector[2]);
+
+      s = s + ds;
+    }
+    t = t + dt;
+  }
+  glEnd();
+}