glmath.h

/*
Copyright (c) 2000-2003 Lee Thomason (www.grinninglizard.com)
Grinning Lizard Utilities.

This software is provided 'as-is', without any express or implied 
warranty. In no event will the authors be held liable for any 
damages arising from the use of this software.

Permission is granted to anyone to use this software for any 
purpose, including commercial applications, and to alter it and 
redistribute it freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must 
not claim that you wrote the original software. If you use this 
software in a product, an acknowledgment in the product documentation 
would be appreciated but is not required.

2. Altered source versions must be plainly marked as such, and 
must not be misrepresented as being the original software.

3. This notice may not be removed or altered from any source 
distribution.
*/


#ifndef GRINLIZ_MATH_INCLUDED
#define GRINLIZ_MATH_INCLUDED

#include <math.h>
#include "glutil.h"

namespace grinliz
{
const float  PI = 3.1415926535897932384626433832795f;
const double PI_D = 3.1415926535897932384626433832795;

const float RAD_TO_DEG = (float)( 360.0 / ( 2.0 * PI ) );
const float DEG_TO_RAD = (float)( ( 2.0 * PI ) / 360.0 );
const float SQRT2 = 1.4142135623730950488016887242097f;
const float SQRT2OVER2 = float( 1.4142135623730950488016887242097 / 2.0 );

const float EPSILON = 0.000001f;

inline bool Equal( float x, float y, float epsilon )
{
        return fabs( (double)(x - y) ) <= (double)epsilon;
}
inline bool Equal( double x, double y, double epsilon )
{
        return fabs( x - y ) <= epsilon;
}

void DegDelta( float angle0, float angle1, float* distance, float* bias );

inline float Length( float x, float y )
{
        // It's worth some time here:
        //              http://www.azillionmonkeys.com/qed/sqroot.html
        // to make this (perhaps) better. 

        // Use the much faster "f" version.
        return sqrtf( x*x + y*y );
}

inline double Length( double x, double y ) 
{ 
        // The more accurate double version.
        return sqrt( x*x + y*y ); 
}

inline float Length( float x, float y, float z )
{
        return sqrtf( x*x + y*y + z*z );
}

inline double Length( double x, double y, double z ) 
{ 
        return sqrt( x*x + y*y + z*z ); 
}

inline float Length( float x, float y, float z, float w )
{
        return sqrtf( x*x + y*y + z*z + w*w );
}


template <class T> inline T FastLength( T x, T y, T z )
{
        float a = (float) fabs( x );
        float b = (float) fabs( y );
        float c = (float) fabs( z );

        if ( b > a ) Swap( &b, &a );
        if ( c > a ) Swap( &c, &a );

        // a, b, and c are now meaningless, but
        // a is the max.

        float ret = a + ( b + c ) / 4;
        return ret;
}


template <class T> inline T FastLength( T x, T y )
{
        float a = (float) fabs( x );
        float b = (float) fabs( y );

        if ( b > a ) grinliz::Swap( &b, &a );

        // a and b are now meaningless, but
        // a is the max.

        float ret = a + b / 4;
        return ret;
}

template <class T> inline T Average( T y0, T y1 )
{
        return ( y0 + y1 ) / T( 2 );
}



};      // namespace grinliz

#endif

---