2 files changed, 89 insertions, 0 deletions
diff --git a/src/utils/mathutils.cpp b/src/utils/mathutils.cpp
new file mode 100644
index 00000000..0ad8f3fb
--- /dev/null
+++ b/src/utils/mathutils.cpp
@@ -0,0 +1,58 @@
+/*
+ *  The Mana World
+ *  Copyright (C) 2009  The Mana World Development Team
+ *
+ *  This file is part of The Mana World.
+ *
+ *  This program 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 2 of the License, or
+ *  any later version.
+ *
+ *  This program 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 more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "utils/mathutils.h"
+
+/* A very fast function to calculate the approximate inverse square root of a
+ * floating point value and a helper function that uses it for getting the
+ * normal squareroot. For an explanation of the inverse squareroot function
+ * read:
+ * http://www.math.purdue.edu/~clomont/Math/Papers/2003/InvSqrt.pdf
+ *
+ * Unfortunately the original creator of this function seems to be unknown.
+ */
+
+float fastInvSqrt(float x)
+{
+    union { int i; float x; } tmp;
+    float xhalf = 0.5f * x;
+    tmp.x = x;
+    tmp.i = 0x5f375a86 - (tmp.i >> 1);
+    x = tmp.x;
+    x = x * (1.5f - xhalf * x * x);
+    return x;
+}
+
+float fastSqrt(float x)
+{
+    return 1.0f / fastInvSqrt(x);
+}
+
+float weightedAverage(float n1, float n2, float w)
+{
+    if (w < 0.0f)
+        return n1;
+
+    if (w > 1.0f)
+        return n2;
+
+    return (w * n2 + (1.0f - w) * n1) / 2.0f;
+}
diff --git a/src/utils/mathutils.h b/src/utils/mathutils.h
new file mode 100644
index 00000000..1b68f223
--- /dev/null
+++ b/src/utils/mathutils.h
@@ -0,0 +1,31 @@
+/*
+ *  The Mana World
+ *  Copyright (C) 2009  The Mana World Development Team
+ *
+ *  This file is part of The Mana World.
+ *
+ *  This program 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 2 of the License, or
+ *  any later version.
+ *
+ *  This program 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 more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef UTILS_MATHUTILS_H
+#define UTILS_MATHUTILS_H
+
+float fastInvSqrt(float x);
+
+float fastSqrt(float x);
+
+float weightedAverage(float n1, float n2, float w);
+
+#endif // UTILS_MATHUTILS_H