slerp.hpp

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#pragma once
#ifndef OGLPLUS_MATH_SLERP_1310291021_HPP
#define OGLPLUS_MATH_SLERP_1310291021_HPP

#include <oglplus/config/compiler.hpp>
#include <oglplus/math/angle.hpp>

namespace oglplus {


template <typename Value, typename T>
class BaseSLERP
{
private:
    Value _v1, _v2;
    Angle<T> _omega;
    T _inv_sin_omega;

    Value _first(T) const
    {
        return _v1;
    }

    Value _lerp(T t) const
    {
        return _v1*(T(1)-t) + _v2*t;
    }

    Value _slerp(T t) const
    {
        return  _v1*Sin((T(1)-t)*_omega)*_inv_sin_omega+
            _v2*Sin(t*_omega)*_inv_sin_omega;
    }

    Value (BaseSLERP::*_func)(T) const;
public:

    BaseSLERP(
        const Value& v1,
        const Value& v2,
        T eps
    ): _v1(v1)
     , _v2(v2)
     , _omega(Angle<T>::ArcCos(Dot(_v1, _v2)))
     , _inv_sin_omega(Sin(_omega))
     , _func(nullptr)
    {
        if(_inv_sin_omega == T(0))
        {
            _func = &BaseSLERP::_first;
        }
        else if(std::abs(_inv_sin_omega) < eps)
        {
            _func = &BaseSLERP::_lerp;
        }
        else
        {
            _func = &BaseSLERP::_slerp;
            _inv_sin_omega = T(1)/_inv_sin_omega;
        }
        assert(_func != nullptr);
    }


    Value operator()(T param) const
    {
        assert(_func != nullptr);
        return (this->*_func)(param);
    }
};

} // namespace oglplus

#endif // include guard