CosinusInterpolator.h

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#pragma once

#include "IInterpolator.h"

#define _USE_MATH_DEFINES
#include <math.h>


template< typename KeyType >
class CosinusInterpolator : public IInterpolator< KeyType >
{
private:
protected:
public:
    explicit        CosinusInterpolator     () = default;
    explicit        CosinusInterpolator     ( const Key< KeyType >& leftKey,
                                              const Key< KeyType >& rightKey,
                                              UPtr< const IInterpolator< KeyType > >& leftInterpolator,
                                              UPtr< const IInterpolator< KeyType > >& rightInterpolator );
                    ~CosinusInterpolator    () = default;


    virtual KeyType         Interpolate     ( TimeType time, Key< KeyType >& left, Key< KeyType >& right ) override;

    virtual void            Update          ( const Key< KeyType >& leftKey,
                                              const Key< KeyType >& rightKey,
                                              UPtr< const IInterpolator< KeyType > >& leftInterpolator,
                                              UPtr< const IInterpolator< KeyType > >& rightInterpolator ) override;

    virtual KeyType         LeftTangent     ( const Key< KeyType >& left, const Key< KeyType >& right ) const override;
    virtual KeyType         RightTangent    ( const Key< KeyType >& left, const Key< KeyType >& right ) const override;
};


//====================================================================================//
//          Implementation  
//====================================================================================//

// ================================ //
//
template< typename KeyType >
inline              CosinusInterpolator< KeyType >::CosinusInterpolator ( const Key< KeyType >& leftKey,
                                                                          const Key< KeyType >& rightKey,
                                                                          UPtr< const IInterpolator< KeyType > >& leftInterpolator,
                                                                          UPtr< const IInterpolator< KeyType >> & rightInterpolator )
{}


// ================================ //
//
template< typename KeyType >
inline KeyType          CosinusInterpolator< KeyType >::Interpolate     ( TimeType time, Key< KeyType >& left, Key< KeyType >& right )
{
    TimeType timeInterval = right.Time - left.Time;
    TimeType progress = ( time - left.Time ) / timeInterval;

    progress = 0.5 + 0.5 * cos( progress * M_PI );

    auto leftResult = ( 1.0 + (-1.0f) * progress ) * left.Value;    // Multiply by -1.0f to avoid calling operator-
    auto rightResult = progress * right.Value;

    return static_cast< KeyType >( leftResult + rightResult );
}

// ================================ //
//
template< typename KeyType >
inline void             CosinusInterpolator< KeyType >::Update          ( const Key< KeyType >& leftKey,
                                                                          const Key< KeyType >& rightKey,
                                                                          UPtr< const IInterpolator< KeyType > >& leftInterpolator,
                                                                          UPtr< const IInterpolator< KeyType > >& rightInterpolator )
{}

// ================================ //
//
template< typename KeyType >
inline KeyType          CosinusInterpolator< KeyType >::LeftTangent     ( const Key< KeyType >& left, const Key< KeyType >& right ) const
{
    return KeyType( 0 );
}

// ================================ //
//
template< typename KeyType >
inline KeyType          CosinusInterpolator< KeyType >::RightTangent    ( const Key< KeyType >& left, const Key< KeyType >& right ) const
{
    return KeyType( 0 );
}