1 files changed, 93 insertions, 0 deletions
diff --git a/libdimension/cylinder.c b/libdimension/cylinder.c
new file mode 100644
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--- /dev/null
+++ b/libdimension/cylinder.c
@@ -0,0 +1,93 @@
+/*************************************************************************
+ * Copyright (C) 2009-2010 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 <math.h>
+
+/*
+ * Cylinder
+ */
+
+/* Cylinder callbacks */
+static bool dmnsn_cylinder_intersection_fn(const dmnsn_object *cylinder,
+                                           dmnsn_line line,
+                                           dmnsn_intersection *intersection);
+static bool dmnsn_cylinder_inside_fn(const dmnsn_object *cylinder,
+                                     dmnsn_vector point);
+
+/* Allocate a new cylinder object */
+dmnsn_object *
+dmnsn_new_cylinder()
+{
+  dmnsn_object *cylinder = dmnsn_new_object();
+  cylinder->intersection_fn  = &dmnsn_cylinder_intersection_fn;
+  cylinder->inside_fn        = &dmnsn_cylinder_inside_fn;
+  cylinder->bounding_box.min = dmnsn_new_vector(-1.0, -1.0, -1.0);
+  cylinder->bounding_box.max = dmnsn_new_vector(1.0, 1.0, 1.0);
+  return cylinder;
+}
+
+/* Intersections callback for a cylinder */
+static bool
+dmnsn_cylinder_intersection_fn(const dmnsn_object *cylinder, dmnsn_line line,
+                               dmnsn_intersection *intersection)
+{
+  dmnsn_line l = dmnsn_transform_line(cylinder->trans_inv, line);
+
+  /* Solve (x0 + nx*t)^2 + (z0 + nz*t)^2 == 1 */
+  double a, b, c, t;
+  a = l.n.x*l.n.x + l.n.z*l.n.z;
+  b = 2.0*(l.n.x*l.x0.x + l.n.z*l.x0.z);
+  c = l.x0.x*l.x0.x + l.x0.z*l.x0.z - 1.0;
+
+
+  if (b*b - 4.0*a*c >= 0.0) {
+    t = (-b - sqrt(b*b - 4.0*a*c))/(2.0*a);
+    dmnsn_vector p = dmnsn_line_point(l, t);
+
+    if (t < 0.0 || p.y <= -1.0 || p.y >= 1.0) {
+      t = (-b + sqrt(b*b - 4.0*a*c))/(2.0*a);
+      p = dmnsn_line_point(l, t);
+
+      if (t < 0.0 || p.y <= -1.0 || p.y >= 1.0)
+        return false;
+    }
+
+    p.y = 0;
+
+    intersection->ray      = line;
+    intersection->t        = t;
+    intersection->normal   = dmnsn_transform_normal(cylinder->trans, p);
+    intersection->texture  = cylinder->texture;
+    intersection->interior = cylinder->interior;
+    return true;
+  }
+
+  return false;
+}
+
+/* Inside callback for a cylinder */
+static bool
+dmnsn_cylinder_inside_fn(const dmnsn_object *cylinder, dmnsn_vector point)
+{
+  point = dmnsn_transform_vector(cylinder->trans_inv, point);
+  return point.x*point.x + point.z*point.z < 1
+      && point.y > -1.0 && point.y < 1.0;
+}