Sphere and cube C++ wrappers.

1 files changed, 181 insertions, 0 deletions

diff --git a/libdimension/objects.c b/libdimension/objects.c
new file mode 100644
index 0000000..b5cf64c
--- /dev/null
+++ b/libdimension/objects.c
@@ -0,0 +1,181 @@
+/*************************************************************************
+ * 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   */
+
+/*
+ * Sphere
+ */
+
+/* Sphere object callbacks */
+static dmnsn_array *dmnsn_sphere_intersections_fn(const dmnsn_object *sphere,
+                                                  dmnsn_line line);
+static int dmnsn_sphere_inside_fn(const dmnsn_object *sphere,
+                                  dmnsn_vector point);
+
+/* Allocate a new sphere */
+dmnsn_object *
+dmnsn_new_sphere()
+{
+  dmnsn_object *sphere = dmnsn_new_object();
+  if (sphere) {
+    sphere->intersections_fn = &dmnsn_sphere_intersections_fn;
+    sphere->inside_fn        = &dmnsn_sphere_inside_fn;
+  }
+  return sphere;
+}
+
+/* Free a sphere */
+void
+dmnsn_delete_sphere(dmnsn_object *sphere)
+{
+  dmnsn_delete_object(sphere);
+}
+
+/* Return a list of insersections of `line' with a sphere */
+static dmnsn_array *
+dmnsn_sphere_intersections_fn(const dmnsn_object *sphere, 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;
+}
+
+/* Return whether a point is inside a sphere (x**2 + y**2 + z**2 < 1.0) */
+static int
+dmnsn_sphere_inside_fn(const dmnsn_object *sphere, dmnsn_vector point)
+{
+  return point.x*point.x + point.y*point.y + point.z*point.z < 1.0;
+}
+
+/*
+ * Cube
+ */
+
+/* Cube callbacks */
+static dmnsn_array *dmnsn_cube_intersections_fn(const dmnsn_object *cube,
+                                                  dmnsn_line line);
+static int dmnsn_cube_inside_fn(const dmnsn_object *cube,
+                                  dmnsn_vector point);
+
+/* Allocate a new cube object */
+dmnsn_object *
+dmnsn_new_cube()
+{
+  dmnsn_object *cube = dmnsn_new_object();
+  if (cube) {
+    cube->intersections_fn = &dmnsn_cube_intersections_fn;
+    cube->inside_fn        = &dmnsn_cube_inside_fn;
+  }
+  return cube;
+}
+
+/* Delete a cube */
+void
+dmnsn_delete_cube(dmnsn_object *cube)
+{
+  dmnsn_delete_object(cube);
+}
+
+/* Intersections callback for a cube */
+static dmnsn_array *
+dmnsn_cube_intersections_fn(const dmnsn_object *cube, dmnsn_line line)
+{
+  double t;
+  dmnsn_vector p;
+  dmnsn_array *array = dmnsn_new_array(sizeof(double));
+
+  /* Six ray-plane intersection tests (x, y, z) = +/- 1.0 */
+
+  if (line.n.x != 0.0) {
+    /* x = -1.0 */
+    t = (-1.0 - line.x0.x)/line.n.x;
+    p = dmnsn_line_point(line, t);
+    if (p.y >= -1.0 && p.y <= 1.0 && p.z >= -1.0 && p.z <= 1.0) {
+      dmnsn_array_push(array, &t);
+    }
+
+    /* x = 1.0 */
+    t = (1.0 - line.x0.x)/line.n.x;
+    p = dmnsn_line_point(line, t);
+    if (p.y >= -1.0 && p.y <= 1.0 && p.z >= -1.0 && p.z <= 1.0) {
+      dmnsn_array_push(array, &t);
+    }
+  }
+
+  if (line.n.y != 0.0) {
+    /* y = -1.0 */
+    t = (-1.0 - line.x0.y)/line.n.y;
+    p = dmnsn_line_point(line, t);
+    if (p.x >= -1.0 && p.x <= 1.0 && p.z >= -1.0 && p.z <= 1.0) {
+      dmnsn_array_push(array, &t);
+    }
+
+    /* y = 1.0 */
+    t = (1.0 - line.x0.y)/line.n.y;
+    p = dmnsn_line_point(line, t);
+    if (p.x >= -1.0 && p.x <= 1.0 && p.z >= -1.0 && p.z <= 1.0) {
+      dmnsn_array_push(array, &t);
+    }
+  }
+
+  if (line.n.z != 0.0) {
+    /* z = -1.0 */
+    t = (-1.0 - line.x0.z)/line.n.z;
+    p = dmnsn_line_point(line, t);
+    if (p.x >= -1.0 && p.x <= 1.0 && p.y >= -1.0 && p.y <= 1.0) {
+      dmnsn_array_push(array, &t);
+    }
+
+    /* z = 1.0 */
+    t = (1.0 - line.x0.z)/line.n.z;
+    p = dmnsn_line_point(line, t);
+    if (p.x >= -1.0 && p.x <= 1.0 && p.y >= -1.0 && p.y <= 1.0) {
+      dmnsn_array_push(array, &t);
+    }
+  }
+
+  return array;
+}
+
+/* Inside callback for a cube */
+static int
+dmnsn_cube_inside_fn(const dmnsn_object *cube, dmnsn_vector point)
+{
+  return point.x > -1.0 && point.x < 1.0
+      && point.y > -1.0 && point.y < 1.0
+      && point.z > -1.0 && point.z < 1.0;
+}