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/*
* 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>
#include <float.h>
#define MATH_UTILS_MAX_ANGLE 360
float sinList[MATH_UTILS_MAX_ANGLE];
float cosList[MATH_UTILS_MAX_ANGLE];
float tanList[MATH_UTILS_MAX_ANGLE];
/*
* 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;
}
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 = M_PI_2 / 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] = FLT_MAX; // approximately infinity
continue;
}
if (i == 270)
{
tanList[i] = -FLT_MAX; // 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];
}
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