1 files changed, 79 insertions, 0 deletions
diff --git a/src/fdgl.hpp b/src/fdgl.hpp
new file mode 100644
index 0000000..6bdb2e7
--- /dev/null
+++ b/src/fdgl.hpp
@@ -0,0 +1,79 @@
+/* This file is part of Ganv.
+ * Copyright 2007-2013 David Robillard <http://drobilla.net>
+ *
+ * Ganv is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or any later version.
+ *
+ * Ganv 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 General Public License for details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Ganv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <float.h>
+#include <math.h>
+
+static const double SPRING_K    = 50.0;
+static const double SPRING_LEN  = 1.0;
+static const double CHARGE_KE   = 50000.0;
+static const double AREA_WEIGHT = 0.25;
+
+inline Vector
+vec_add(const Vector& a, const Vector& b)
+{
+	const Vector result = { a.x + b.x, a.y + b.y };
+	return result;
+}
+
+inline Vector
+vec_sub(const Vector& a, const Vector& b)
+{
+	const Vector result = { a.x - b.x, a.y - b.y };
+	return result;
+}
+
+inline Vector
+vec_mult(const Vector& a, double m)
+{
+	const Vector result = { a.x * m, a.y * m };
+	return result;
+}
+
+inline double
+vec_mult(const Vector& a, const Vector& b)
+{
+	return a.x * b.x + a.y * b.y;
+}
+
+/** Reciprocal of magnitude. */
+inline double
+vec_rmag(const Vector& vec)
+{
+	return 1.0 / sqrt(vec.x * vec.x + vec.y * vec.y);
+}
+
+/** Hooke's law */
+inline Vector
+spring_force(const Vector& a, const Vector& b)
+{
+	const Vector vec          = vec_sub(b, a);
+	const double rmag         = vec_rmag(vec);
+	const double displacement = SPRING_LEN - (1.0 / rmag);
+	return vec_mult(vec, rmag * SPRING_K * displacement * 0.5);
+}
+
+/** Modified Coulomb's law */
+inline Vector
+repel_force(const Vector& a, const Vector& a_area,
+            const Vector& b, const Vector& b_area)
+{
+	const Vector vec      = vec_sub(a, b);
+	const double rmag     = vec_rmag(vec);
+	const Vector a_weight = vec_mult(a_area, AREA_WEIGHT);
+	const Vector b_weight = vec_mult(b_area, AREA_WEIGHT);
+	const Vector force    = vec_mult(vec, rmag * rmag * rmag * CHARGE_KE * 0.5);
+	return vec_mult(force, vec_mult(a_weight, b_weight));
+}