trajectory.hpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef ANTKEEPER_PHYSICS_ORBIT_TRAJECTORY_HPP
#define ANTKEEPER_PHYSICS_ORBIT_TRAJECTORY_HPP
 
#include <engine/math/polynomial.hpp>
#include <engine/math/vector.hpp>
#include <vector>
 
namespace physics {
namespace orbit {
 
template <class T>
struct trajectory
{
    T t0;
    
    T t1;
    
    T dt;
    
    std::size_t n;
    
    std::vector<T> a;
    
    [[nodiscard]] math::vec3<T> position(T t) const;
};
 
template <class T>
math::vec3<T> trajectory<T>::position(T t) const
{
    t -= t0;
    std::size_t i = static_cast<std::size_t>(t / dt);
    
    const T* ax = &a[i * n * 3];
    const T* ay = ax + n;
    const T* az = ay + n;
    
    t = (t / dt - i) * T(2) - T(1);
    
    math::vec3<T> r;
    r.x() = math::polynomial::chebyshev::evaluate(ax, ay, t);
    r.y() = math::polynomial::chebyshev::evaluate(ay, az, t);
    r.z() = math::polynomial::chebyshev::evaluate(az, az + n, t);
    
    return r;
}
 
} // namespace orbit
} // namespace physics
 
#endif // ANTKEEPER_PHYSICS_ORBIT_TRAJECTORY_HPP