1 files changed, 69 insertions, 0 deletions
diff --git a/libdimension/sphere.c b/libdimension/sphere.c
new file mode 100644
index 0000000..4b99eaf
--- /dev/null
+++ b/libdimension/sphere.c
@@ -0,0 +1,69 @@
+/*************************************************************************
+ * Copyright (C) 2008 Tavian Barnes <tavianator@gmail.com>               *
+ *                                                                       *
+ * This file is part of The Dimension Library.                           *
+ *                                                                       *
+ * The Dimension Library is free software; you can redistribute it and/  *
+ * or modify it under the terms of the GNU Lesser General Public License *
+ * as published by the Free Software Foundation; either version 3 of the *
+ * License, or (at your option) any later version.                       *
+ *                                                                       *
+ * The Dimension Library is distributed in the hope that it will be      *
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty   *
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU  *
+ * Lesser General Public License for more details.                       *
+ *                                                                       *
+ * You should have received a copy of the GNU Lesser General Public      *
+ * License along with this program.  If not, see                         *
+ * <http://www.gnu.org/licenses/>.                                       *
+ *************************************************************************/
+
+#include "dimension.h"
+#include <stdlib.h> /* For malloc */
+#include <math.h>   /* For sqrt   */
+
+static dmnsn_array *dmnsn_sphere_intersections_fn(dmnsn_line line);
+static int dmnsn_sphere_inside_fn(dmnsn_vector point);
+
+dmnsn_object *
+dmnsn_new_sphere()
+{
+  dmnsn_object *sphere = dmnsn_new_object();
+  sphere->intersections_fn = &dmnsn_sphere_intersections_fn;
+  sphere->inside_fn        = &dmnsn_sphere_inside_fn;
+  return sphere;
+}
+
+void
+dmnsn_delete_sphere(dmnsn_object *sphere)
+{
+  dmnsn_delete_object(sphere);
+}
+
+static dmnsn_array *
+dmnsn_sphere_intersections_fn(dmnsn_line line)
+{
+  double a, b, c, t[2];
+  dmnsn_array *array = dmnsn_new_array(sizeof(double));
+
+  // Solve (x0 + nx*t)^2 + (y0 + ny*t)^2 + (z0 + nz*t)^2 == 1
+
+  a = line.n.x*line.n.x + line.n.y*line.n.y + line.n.z*line.n.z;
+  b = 2.0*(line.n.x*line.x0.x + line.n.y*line.x0.y + line.n.z*line.x0.z);
+  c = line.x0.x*line.x0.x + line.x0.y*line.x0.y + line.x0.z*line.x0.z - 1.0;
+
+  if (b*b - 4.0*a*c >= 0) {
+    t[0] = (-b + sqrt(b*b - 4.0*a*c))/(2*a);
+    t[1] = (-b - sqrt(b*b - 4.0*a*c))/(2*a);
+    dmnsn_array_set(array, 0, &t[0]);
+    dmnsn_array_set(array, 1, &t[1]);
+  }
+
+  return array;
+}
+
+static int
+dmnsn_sphere_inside_fn(dmnsn_vector point)
+{
+  return sqrt(point.x*point.x + point.y*point.y + point.z*point.z) < 1.0;
+}