CWE-ou-minkata/Sources/Plasma/PubUtilLib/plDrawable/plTimedInterp.h

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*==LICENSE==*/

#ifndef plTimedInterp_inc
#define plTimedInterp_inc

// There's no auto update on this, the owner is
// required to call update periodically.
//
// This isn't optimized in any way, and is still
// fairly general. Adding features would most likely
// be best implemented in a derived type.
// Notably lacking features are:
//      ability to read and write, 
//      auto-eval on significant time change
//      
//
// Requires class T to have the following members
// T& operator+=(const class T& t);
// T& operator-=(const class T& t);
// T& operator*=(float scale);
// T& operator=(const class T&); // unless builtin = is adequate.
//
template <class T> class plTimedInterp
{
protected:
    T           fInit;
    T           fCurr;
    T           fTarg;

    double      fDuration;
    double      fEnd;

    const T& IEnd();
    const T& IBegin();
    const T& IEval(float parm);
public:
    plTimedInterp();
    plTimedInterp(const T& t);

    const T& Set(const T& val) { return SetTarget(val, 0, 0); }
    const T& SetTarget(const T& targ, double start, double duration);

    const T& Update(double t);

    operator T() const { return fCurr; }
    const T& Value() const { return fCurr; }
};

template <class T>
plTimedInterp<T>::plTimedInterp()
:   fDuration(0),
    fEnd(0)
{
}

template <class T>
plTimedInterp<T>::plTimedInterp(const T& t)
:   fInit(t),
    fCurr(t),
    fTarg(t),
    fDuration(0),
    fEnd(0)
{
}

template <class T>
const T& 
plTimedInterp<T>::Update(double t)
{
    if( fDuration <= 0 )
        return IEnd();

    float parm = float((fEnd - t) / fDuration);
    if( parm <= 0 )
        return IEnd();
    else if( parm >= 1.f )
        return IBegin();

    return IEval(parm);
}

template <class T>
const T& 
plTimedInterp<T>::SetTarget(const T& targ, double start, double dur)
{
    fEnd = start + dur;
    fDuration = dur;
    fTarg = targ;
    if( dur <= 0 )
        fCurr = targ;
    fInit = fCurr;
    return fCurr;
}

template <class T>
const T& 
plTimedInterp<T>::IEnd()
{
    fDuration = 0;
    fCurr = fTarg;
    return fCurr;
}

template <class T>
const T& 
plTimedInterp<T>::IBegin()
{
    return fCurr;
}

template <class T>
const T& 
plTimedInterp<T>::IEval(float parm)
{
    fCurr = fInit;
    fCurr -= fTarg;
    fCurr *= parm;
    fCurr += fTarg;
    return fCurr;
}


#endif // plTimedInterp_inc