warzone2100/lib/framework/trig.c

183 lines
3.5 KiB
C

/*
This file is part of Warzone 2100.
Copyright (C) 1999-2004 Eidos Interactive
Copyright (C) 2005-2007 Warzone Resurrection Project
Warzone 2100 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
(at your option) any later version.
Warzone 2100 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 Warzone 2100; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* Trig.c
*
* Trig lookup tables
*
*/
/* Allow frame header files to be singly included */
#define FRAME_LIB_INCLUDE
#include <assert.h>
#include <stdlib.h>
#include <math.h>
#include "types.h"
#include "debug.h"
#include "trig.h"
/* Number of steps between -1 and 1 for the inverse tables */
#define TRIG_ACCURACY 4096
#define TRIG_ACCMASK 0x0fff
/* Number of entries in sqrt table */
#define SQRT_ACCURACY 4096
#define SQRT_ACCBITS 12
static float aSin[TRIG_DEGREES];
static float aCos[TRIG_DEGREES];
static float aInvCos[TRIG_ACCURACY];
static float aInvSin[TRIG_ACCURACY];
static float aSqrt[SQRT_ACCURACY];
/* Initialise the Trig tables */
BOOL trigInitialise(void)
{
float val = 0.0f, inc = 2.0f * M_PI / TRIG_DEGREES;
int i;
// Initialise the tables
for (i = 0; i < TRIG_DEGREES; i++)
{
aSin[i] = sinf(val);
aCos[i] = cosf(val);
val += inc;
}
inc = 2.0f / (TRIG_ACCURACY-1);
val = -1;
for (i = 0; i < TRIG_ACCURACY; i++)
{
aInvSin[i] = asinf(val) * (float)TRIG_DEGREES / (2.0f * (float)M_PI);
aInvCos[i] = acosf(val) * (float)TRIG_DEGREES / (2.0f * (float)M_PI);
val += inc;
}
for (i = 0; i < SQRT_ACCURACY; i++)
{
val = (float)i / (SQRT_ACCURACY / 2);
aSqrt[i]= sqrtf(val);
}
return TRUE;
}
/* Shutdown the trig tables */
void trigShutDown(void)
{}
/* Access the trig tables */
float trigSin(int angle)
{
if (angle < 0)
{
angle = (-angle) % TRIG_DEGREES;
angle = TRIG_DEGREES - angle;
}
else
{
angle = angle % TRIG_DEGREES;
}
return aSin[angle % TRIG_DEGREES];
}
float trigCos(int angle)
{
if (angle < 0)
{
angle = (-angle) % TRIG_DEGREES;
angle = TRIG_DEGREES - angle;
}
else
{
angle = angle % TRIG_DEGREES;
}
return aCos[angle % TRIG_DEGREES];
}
float trigInvSin(float val)
{
SDWORD index = (val+1) * (TRIG_ACCURACY-1) / 2;
return aInvSin[index & TRIG_ACCMASK];
}
float trigInvCos(float val)
{
SDWORD index = (val+1) * (TRIG_ACCURACY-1) / 2;
return aInvCos[index & TRIG_ACCMASK];
}
/* Fast lookup sqrt */
float trigIntSqrt(unsigned int val)
{
UDWORD exp, mask;
if (val == 0)
{
return 0.0f;
}
// find the exponent of the number
mask = 0x80000000; // set the msb in the mask
for(exp = 32; exp != 0; exp--)
{
if (val & mask)
{
break;
}
mask >>= 1;
}
// make all exponents even
// odd exponents result in a mantissa of [1..2) rather than [0..1)
if (exp & 1)
{
exp -= 1;
}
// need to shift the top bit to SQRT_BITS - left or right?
if (exp >= SQRT_ACCBITS)
{
val >>= exp - SQRT_ACCBITS + 1;
}
else
{
val <<= SQRT_ACCBITS - 1 - exp;
}
// now generate the fractional part for the lookup table
ASSERT( val < SQRT_ACCURACY, "trigIntSqrt: table index out of range" );
return aSqrt[val] * (1 << (exp/2));
}