From cdf81ef8e5b25fd8751a92c6ff394c01daedbb88 Mon Sep 17 00:00:00 2001
From: Rogier Polak <rogier.l.a.polak@gmail.com>
Date: Sat, 3 Mar 2007 03:32:46 +0000
Subject: Implemented an alternate collision-detection function, added
 namespace utils::math.

---
 src/utils/mathutils.cpp | 106 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100644 src/utils/mathutils.cpp

(limited to 'src/utils/mathutils.cpp')

diff --git a/src/utils/mathutils.cpp b/src/utils/mathutils.cpp
new file mode 100644
index 00000000..0a46ff2c
--- /dev/null
+++ b/src/utils/mathutils.cpp
@@ -0,0 +1,106 @@
+/*
+ *  The Mana World Server
+ *  Copyright 2004 The Mana World Development Team
+ *
+ *  This file is part of The Mana World.
+ *
+ *  The Mana World  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.
+ *
+ *  The Mana  World 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 The Mana  World; if not, write to the  Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ *  $Id: $
+ */
+
+#include "mathutils.h"
+
+#include <cmath>
+
+#define MATH_UTILS_MAX_ANGLE 360
+
+float sinList[MATH_UTILS_MAX_ANGLE];
+float cosList[MATH_UTILS_MAX_ANGLE];
+float tanList[MATH_UTILS_MAX_ANGLE];
+
+/**
+ * fastInvSqrt:
+ *
+ * A very fast function to calculate the approximate inverse square root of a
+ * floating point value. 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.
+ *
+ * TODO: - Make this function run on 64-bit architectures
+ *       - Find out and fix why this function fails when compiled with the -O2
+ *         optimization flag on
+ *         gcc version 4.0.2 20050808 (prerelease) (Ubuntu 4.0.1-4ubuntu9).
+ */
+float utils::math::fastInvSqrt(float x)
+{
+    float xhalf = 0.5f*x;
+    int i = *(int*)&x;
+    i = 0x5f375a86- (i>>1);
+    x = *(float*)&i;
+    x = x*(1.5f-xhalf*x*x);
+    return x;
+}
+
+/**
+ * fastSqrt:
+ *
+ * A helper function that uses the fastInvSqrt for getting the
+ * normal squareroot.
+ */
+float utils::math::fastSqrt(float x)
+{
+    return 1.0f/utils::math::fastInvSqrt(x);
+}
+
+void utils::math::init()
+{
+    // Constant for calculating an angle in radians out of an angle in degrees
+    const float radianAngleRatio = acos(0.0f) / 90.0f; // pi/2 / 90[deg]
+
+    for(int i = 0; i < MATH_UTILS_MAX_ANGLE; i++)
+    {
+        sinList[i] = sin(radianAngleRatio * (float)i);
+        cosList[i] = cos(radianAngleRatio * (float)i);
+
+        if (i == 90)
+        {
+            tanList[i] = 1.0E40f; //approximately infinity
+            continue;
+        }
+        if (i == 270)
+        {
+            tanList[i] = -1.0E40f; //approximately infinity
+            continue;
+        }
+        tanList[i] = tan(radianAngleRatio * (float)i);
+    }
+}
+
+float utils::math::cachedSin(int angle)
+{
+    return sinList[angle];
+}
+
+float utils::math::cachedCos(int angle)
+{
+    return cosList[angle];
+}
+
+float utils::math::cachedTan(int angle)
+{
+    return tanList[angle];
+}
-- 
cgit v1.2.3-70-g09d2