mirror of
https://github.com/dhewm/dhewm3.git
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131 lines
4.9 KiB
C++
131 lines
4.9 KiB
C++
/*
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===========================================================================
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Doom 3 GPL Source Code
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Copyright (C) 1999-2011 id Software LLC, a ZeniMax Media company.
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This file is part of the Doom 3 GPL Source Code ("Doom 3 Source Code").
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Doom 3 Source Code 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 3 of the License, or
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(at your option) any later version.
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Doom 3 Source Code 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 Doom 3 Source Code. If not, see <http://www.gnu.org/licenses/>.
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In addition, the Doom 3 Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 Source Code. If not, please request a copy in writing from id Software at the address below.
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If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.
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===========================================================================
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*/
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#include "../precompiled.h"
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#pragma hdrstop
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const float idMath::PI = 3.14159265358979323846f;
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const float idMath::TWO_PI = 2.0f * PI;
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const float idMath::HALF_PI = 0.5f * PI;
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const float idMath::ONEFOURTH_PI = 0.25f * PI;
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const float idMath::E = 2.71828182845904523536f;
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const float idMath::SQRT_TWO = 1.41421356237309504880f;
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const float idMath::SQRT_THREE = 1.73205080756887729352f;
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const float idMath::SQRT_1OVER2 = 0.70710678118654752440f;
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const float idMath::SQRT_1OVER3 = 0.57735026918962576450f;
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const float idMath::M_DEG2RAD = PI / 180.0f;
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const float idMath::M_RAD2DEG = 180.0f / PI;
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const float idMath::M_SEC2MS = 1000.0f;
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const float idMath::M_MS2SEC = 0.001f;
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const float idMath::INFINITY = 1e30f;
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const float idMath::FLT_EPSILON = 1.192092896e-07f;
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bool idMath::initialized = false;
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dword idMath::iSqrt[SQRT_TABLE_SIZE]; // inverse square root lookup table
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/*
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===============
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idMath::Init
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===============
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*/
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void idMath::Init( void ) {
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union _flint fi, fo;
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for ( int i = 0; i < SQRT_TABLE_SIZE; i++ ) {
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fi.i = ((EXP_BIAS-1) << EXP_POS) | (i << LOOKUP_POS);
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fo.f = (float)( 1.0 / sqrt( fi.f ) );
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iSqrt[i] = ((dword)(((fo.i + (1<<(SEED_POS-2))) >> SEED_POS) & 0xFF))<<SEED_POS;
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}
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iSqrt[SQRT_TABLE_SIZE / 2] = ((dword)(0xFF))<<(SEED_POS);
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initialized = true;
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}
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/*
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================
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idMath::FloatToBits
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================
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*/
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int idMath::FloatToBits( float f, int exponentBits, int mantissaBits ) {
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int i, sign, exponent, mantissa, value;
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assert( exponentBits >= 2 && exponentBits <= 8 );
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assert( mantissaBits >= 2 && mantissaBits <= 23 );
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int maxBits = ( ( ( 1 << ( exponentBits - 1 ) ) - 1 ) << mantissaBits ) | ( ( 1 << mantissaBits ) - 1 );
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int minBits = ( ( ( 1 << exponentBits ) - 2 ) << mantissaBits ) | 1;
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float max = BitsToFloat( maxBits, exponentBits, mantissaBits );
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float min = BitsToFloat( minBits, exponentBits, mantissaBits );
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if ( f >= 0.0f ) {
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if ( f >= max ) {
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return maxBits;
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} else if ( f <= min ) {
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return minBits;
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}
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} else {
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if ( f <= -max ) {
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return ( maxBits | ( 1 << ( exponentBits + mantissaBits ) ) );
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} else if ( f >= -min ) {
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return ( minBits | ( 1 << ( exponentBits + mantissaBits ) ) );
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}
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}
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exponentBits--;
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i = *reinterpret_cast<int *>(&f);
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sign = ( i >> IEEE_FLT_SIGN_BIT ) & 1;
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exponent = ( ( i >> IEEE_FLT_MANTISSA_BITS ) & ( ( 1 << IEEE_FLT_EXPONENT_BITS ) - 1 ) ) - IEEE_FLT_EXPONENT_BIAS;
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mantissa = i & ( ( 1 << IEEE_FLT_MANTISSA_BITS ) - 1 );
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value = sign << ( 1 + exponentBits + mantissaBits );
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value |= ( ( INTSIGNBITSET( exponent ) << exponentBits ) | ( abs( exponent ) & ( ( 1 << exponentBits ) - 1 ) ) ) << mantissaBits;
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value |= mantissa >> ( IEEE_FLT_MANTISSA_BITS - mantissaBits );
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return value;
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}
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/*
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================
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idMath::BitsToFloat
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================
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*/
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float idMath::BitsToFloat( int i, int exponentBits, int mantissaBits ) {
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static int exponentSign[2] = { 1, -1 };
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int sign, exponent, mantissa, value;
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assert( exponentBits >= 2 && exponentBits <= 8 );
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assert( mantissaBits >= 2 && mantissaBits <= 23 );
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exponentBits--;
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sign = i >> ( 1 + exponentBits + mantissaBits );
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exponent = ( ( i >> mantissaBits ) & ( ( 1 << exponentBits ) - 1 ) ) * exponentSign[( i >> ( exponentBits + mantissaBits ) ) & 1];
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mantissa = ( i & ( ( 1 << mantissaBits ) - 1 ) ) << ( IEEE_FLT_MANTISSA_BITS - mantissaBits );
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value = sign << IEEE_FLT_SIGN_BIT | ( exponent + IEEE_FLT_EXPONENT_BIAS ) << IEEE_FLT_MANTISSA_BITS | mantissa;
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return *reinterpret_cast<float *>(&value);
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}
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