/home/travis/build/lis-epfl/MAVRIC_Library/util/maths.h

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/*******************************************************************************
 * \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           ///< Declaration of PI for math computation


#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;

     if (angle > 0.0f)
     {
         out = fmod(angle + PI, 2.0f * PI) - PI;
     }
     else
     {
         out = fmod(angle - PI, 2.0f * PI) + PI;
     }

     return out;
 }


float static inline maths_fast_inv_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));
    return y;
}


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;
    }
}


static inline int8_t maths_sign(float x)
{
    if (x >= 0.0f)
    {
        return 1.0f;
    }
    else
    {
        return -1.0f;
    }
}


#ifdef __cplusplus
}
#endif

#endif  /*  MATHS_H  */