Implement triangles.

1 files changed, 83 insertions, 0 deletions

diff --git a/libdimension/triangle.c b/libdimension/triangle.c
new file mode 100644
index 0000000..bd54e1a
--- /dev/null
+++ b/libdimension/triangle.c
@@ -0,0 +1,83 @@
+/*************************************************************************
+ * Copyright (C) 2009-2010 Tavian Barnes <tavianator@tavianator.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/>.                                       *
+ *************************************************************************/
+
+/**
+ * @file
+ * Triangles.
+ */
+
+#include "dimension.h"
+
+typedef struct dmnsn_triangle_payload {
+  dmnsn_vector a, ab, ac, normal;
+} dmnsn_triangle_payload;
+
+/** Triangle intersection callback. */
+static bool
+dmnsn_triangle_intersection_fn(const dmnsn_object *triangle, dmnsn_line l,
+                               dmnsn_intersection *intersection)
+{
+  const dmnsn_triangle_payload *payload = triangle->ptr;
+
+  double den = -dmnsn_vector_dot(l.n, payload->normal);
+  dmnsn_vector ax0 = dmnsn_vector_sub(l.x0, payload->a);
+  double t = dmnsn_vector_dot(ax0, payload->normal)/den;
+  double u = -dmnsn_vector_dot(l.n, dmnsn_vector_cross(ax0, payload->ac))/den;
+  double v = -dmnsn_vector_dot(l.n, dmnsn_vector_cross(payload->ab, ax0))/den;
+  if (t >= 0.0 && u >= 0.0 && v >= 0.0 && u + v <= 1.0) {
+    intersection->ray      = l;
+    intersection->t        = t;
+    intersection->normal   = payload->normal;
+    intersection->texture  = triangle->texture;
+    intersection->interior = triangle->interior;
+    return true;
+  }
+
+  return false;
+}
+
+/** Triangle inside callback. */
+static bool
+dmnsn_triangle_inside_fn(const dmnsn_object *triangle, dmnsn_vector point)
+{
+  return false;
+}
+
+/* Allocate a new triangle */
+dmnsn_object *
+dmnsn_new_triangle(dmnsn_vector a, dmnsn_vector b, dmnsn_vector c)
+{
+  dmnsn_object *triangle = dmnsn_new_object();
+
+  dmnsn_triangle_payload *payload =
+    dmnsn_malloc(sizeof(dmnsn_triangle_payload));
+  payload->a      = a;
+  payload->ab     = dmnsn_vector_sub(b, a);
+  payload->ac     = dmnsn_vector_sub(c, a);
+  payload->normal = dmnsn_vector_cross(payload->ab, payload->ac);
+
+  triangle->ptr              = payload;
+  triangle->intersection_fn  = dmnsn_triangle_intersection_fn;
+  triangle->inside_fn        = dmnsn_triangle_inside_fn;
+  triangle->free_fn          = dmnsn_free;
+  triangle->bounding_box.min = dmnsn_vector_min(dmnsn_vector_min(a, b), c);
+  triangle->bounding_box.max = dmnsn_vector_max(dmnsn_vector_max(a, b), c);
+  return triangle;
+}