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/*
* The Mana Server
* Copyright (C) 2004 The Mana World Development Team
*
* This file is part of The Mana Server.
*
* The Mana Server 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 Server 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 Server. If not, see <http://www.gnu.org/licenses/>.
*/
#include "mathutils.h"
#include <cmath>
#include <stdint.h>
#include <string.h>
#include <float.h>
static const int MATH_UTILS_MAX_ANGLE = 360;
static float sinList[MATH_UTILS_MAX_ANGLE];
static float cosList[MATH_UTILS_MAX_ANGLE];
static float tanList[MATH_UTILS_MAX_ANGLE];
namespace utils {
namespace math {
/*
* 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.
*
* I wholeheartedly disagree with the use of this function -- silene
*/
float fastInvSqrt(float x)
{
typedef char float_must_be_32_bits[(sizeof(float) == 4) * 2 - 1];
float xhalf = 0.5f * x;
uint32_t i;
memcpy(&i, &x, 4);
i = 0x5f375a86 - (i >> 1);
memcpy(&x, &i, 4);
x = x * (1.5f-xhalf * x * x);
return x;
}
void 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 cachedSin(int angle)
{
return sinList[angle];
}
float cachedCos(int angle)
{
return cosList[angle];
}
float cachedTan(int angle)
{
return tanList[angle];
}
} // namespace math
} // namespace utils
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