183 lines
3.5 KiB
C
183 lines
3.5 KiB
C
/*
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This file is part of Warzone 2100.
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Copyright (C) 1999-2004 Eidos Interactive
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Copyright (C) 2005-2007 Warzone Resurrection Project
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Warzone 2100 is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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Warzone 2100 is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Warzone 2100; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/*
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* Trig.c
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*
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* Trig lookup tables
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*
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*/
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/* Allow frame header files to be singly included */
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#define FRAME_LIB_INCLUDE
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#include <assert.h>
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#include <stdlib.h>
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#include <math.h>
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#include "types.h"
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#include "debug.h"
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#include "trig.h"
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/* Number of steps between -1 and 1 for the inverse tables */
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#define TRIG_ACCURACY 4096
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#define TRIG_ACCMASK 0x0fff
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/* Number of entries in sqrt table */
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#define SQRT_ACCURACY 4096
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#define SQRT_ACCBITS 12
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static float aSin[TRIG_DEGREES];
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static float aCos[TRIG_DEGREES];
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static float aInvCos[TRIG_ACCURACY];
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static float aInvSin[TRIG_ACCURACY];
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static float aSqrt[SQRT_ACCURACY];
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/* Initialise the Trig tables */
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BOOL trigInitialise(void)
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{
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float val = 0.0f, inc = 2.0f * M_PI / TRIG_DEGREES;
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int i;
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// Initialise the tables
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for (i = 0; i < TRIG_DEGREES; i++)
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{
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aSin[i] = sinf(val);
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aCos[i] = cosf(val);
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val += inc;
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}
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inc = 2.0f / (TRIG_ACCURACY-1);
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val = -1;
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for (i = 0; i < TRIG_ACCURACY; i++)
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{
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aInvSin[i] = asinf(val) * (float)TRIG_DEGREES / (2.0f * (float)M_PI);
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aInvCos[i] = acosf(val) * (float)TRIG_DEGREES / (2.0f * (float)M_PI);
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val += inc;
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}
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for (i = 0; i < SQRT_ACCURACY; i++)
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{
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val = (float)i / (SQRT_ACCURACY / 2);
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aSqrt[i]= sqrtf(val);
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}
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return true;
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}
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/* Shutdown the trig tables */
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void trigShutDown(void)
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{}
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/* Access the trig tables */
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float trigSin(int angle)
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{
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if (angle < 0)
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{
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angle = (-angle) % TRIG_DEGREES;
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angle = TRIG_DEGREES - angle;
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}
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else
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{
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angle = angle % TRIG_DEGREES;
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}
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return aSin[angle % TRIG_DEGREES];
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}
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float trigCos(int angle)
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{
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if (angle < 0)
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{
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angle = (-angle) % TRIG_DEGREES;
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angle = TRIG_DEGREES - angle;
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}
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else
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{
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angle = angle % TRIG_DEGREES;
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}
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return aCos[angle % TRIG_DEGREES];
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}
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float trigInvSin(float val)
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{
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SDWORD index = (val+1) * (TRIG_ACCURACY-1) / 2;
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return aInvSin[index & TRIG_ACCMASK];
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}
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float trigInvCos(float val)
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{
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SDWORD index = (val+1) * (TRIG_ACCURACY-1) / 2;
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return aInvCos[index & TRIG_ACCMASK];
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}
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/* Fast lookup sqrt */
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float trigIntSqrt(unsigned int val)
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{
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UDWORD exp, mask;
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if (val == 0)
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{
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return 0.0f;
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}
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// find the exponent of the number
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mask = 0x80000000; // set the msb in the mask
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for(exp = 32; exp != 0; exp--)
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{
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if (val & mask)
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{
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break;
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}
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mask >>= 1;
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}
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// make all exponents even
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// odd exponents result in a mantissa of [1..2) rather than [0..1)
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if (exp & 1)
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{
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exp -= 1;
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}
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// need to shift the top bit to SQRT_BITS - left or right?
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if (exp >= SQRT_ACCBITS)
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{
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val >>= exp - SQRT_ACCBITS + 1;
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}
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else
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{
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val <<= SQRT_ACCBITS - 1 - exp;
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}
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// now generate the fractional part for the lookup table
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ASSERT( val < SQRT_ACCURACY, "trigIntSqrt: table index out of range" );
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return aSqrt[val] * (1 << (exp/2));
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}
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