maths.h

/*******************************************************************************
 * Copyright (c) 2009-2014, MAV'RIC Development Team
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice, 
 * this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright notice, 
 * this list of conditions and the following disclaimer in the documentation 
 * and/or other materials provided with the distribution.
 * 
 * 3. Neither the name of the copyright holder nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 ******************************************************************************/

/*******************************************************************************
 * \file maths.h
 * 
 * \author MAV'RIC Team
 * \author Felix Schill
 * \author Geraud L'Eplattenier
 *   
 * \brief Useful math functions
 *
 ******************************************************************************/


#ifndef MATHS_H
#define MATHS_H

#ifdef __cplusplus
extern "C" 
{
#endif

#include <stdint.h>
#include <math.h>

#define PI 3.141592653589793f           


#define MATH_DEG_TO_RAD (PI/180.0f)


#define MATH_RAD_TO_DEG (180.0f/PI)


#define SQR(in) \
        ((in)*(in))


float static inline maths_deg_to_rad(float i)
{
    return MATH_DEG_TO_RAD * i;
}


float static inline maths_rad_to_deg(float i)
{
    return MATH_RAD_TO_DEG * i;
}


float static inline maths_calc_smaller_angle(float angle) 
{
    float out=angle;
    while (out<-PI) out += 2.0f * PI;
    while (out>=PI) out -= 2.0f * PI;
    return out;
}


float static inline maths_fast_sqrt(float number) 
{
    union
    {
        float   f;
        int32_t l;
    }i;
    
    float x, y;
    const float f = 1.5f;

    x = number * 0.5f;
    i.f = number;
    i.l  = 0x5f3759df - ( i.l >> 1 );
    y = i.f;
    y = y * ( f - ( x * y * y ) );
    y = y * ( f - ( x * y * y ) ); // repeat newton iteration for more accuracy
    return number * y;
}


float static inline maths_fast_sqrt_1(float input) 
{
    if (input<0) 
    {
        return 0.0f;
    }

    float result = 1.0f;

    result = 0.5f * (result + (input / result));
    result = 0.5f * (result + (input / result));

    return result;
}


static inline float maths_f_abs(const float a)
{
    if (a >= 0.0f)
    {
        return a;
    }
    else
    {
        return -a;
    }
}


static inline float maths_f_min(const float a, const float b)
{
    if (a <= b)
    {
        return a;
    }
    else
    {
        return b;
    }
}


static inline float maths_f_max(const float a, const float b){
    if (a >= b)
    {
        return a;
    }
    else
    {
        return b;
    }
}


static float inline maths_clip(float input_value, float clip_value) 
{   
    if (input_value>clip_value)  return clip_value;     
    if (input_value<-clip_value) return -clip_value; 
    return input_value;
}


static float inline maths_soft_zone(float x, float soft_zone_width) 
{
    if (soft_zone_width < 0.0000001f) 
    {   
        return x;
    } 
    else 
    {
        return x * x * x / ( SQR(soft_zone_width) + SQR(x) );
    }
};


static float inline maths_sigmoid(float x) 
{
    return (x / maths_fast_sqrt(1 + SQR(x)));
};


static float inline maths_center_window_2(float x) 
{
    return 1.0f / (1 + SQR(x));
}


static float inline maths_center_window_4(float x) 
{
    return 1.0f / (1 + SQR(SQR(x)));
}


static float inline maths_median_filter_3x(float a, float b, float c) 
{
    float middle;
    
    if ((a <= b) && (a <= c)) 
    {
        middle = (b <= c) ? b : c;
    }
    else if ((b <= a) && (b <= c))
    {
        middle = (a <= c) ? a : c;
    } 
    else 
    {
       middle = (a <= b) ? a : b;
    }

    return middle;
}


static inline float maths_interpolate(float x, float x1, float x2, float y1, float y2)
{
    if (x1 == x2)
    {
        return y1;
    }
    else
    {
        float y = y1 + (y2 - y1) * (x - x1) / (x2 - x1); 
        return y;
    }
}


#ifdef __cplusplus
}
#endif

#endif  /*  MATHS_H  */