💿🐜 Antkeeper source code
https://antkeeper.com
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85 lines
2.1 KiB
85 lines
2.1 KiB
/*
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* Copyright (C) 2021 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_PHYSICS_ORBIT_TRAJECTORY_HPP
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#define ANTKEEPER_PHYSICS_ORBIT_TRAJECTORY_HPP
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#include "math/polynomial.hpp"
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#include "math/vector.hpp"
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#include <vector>
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namespace physics {
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namespace orbit {
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/**
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* Describes the trajectory of an orbit with Chebyshev polynomials.
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*
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* @tparam t Real type.
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*/
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template <class T>
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struct trajectory
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{
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/// Start time of the trajectory.
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T t0;
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/// End time of the trajectory.
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T t1;
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/// Time step duration.
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T dt;
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/// Chebyshev polynomial degree.
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std::size_t n;
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/// Chebyshev polynomial coefficients.
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std::vector<T> a;
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/**
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* Calculates the Cartesian position of a trajectory at a given time.
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*
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* @param t Time, on `[t0, t1)`.
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* @return Trajectory position at time @p t.
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*/
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math::vector<T, 3> position(T t) const;
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};
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template <class T>
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math::vector<T, 3> trajectory<T>::position(T t) const
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{
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t -= t0;
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std::size_t i = static_cast<std::size_t>(t / dt);
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const T* ax = &a[i * n * 3];
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const T* ay = ax + n;
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const T* az = ay + n;
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t = (t / dt - i) * T(2) - T(1);
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math::vector3<T> r;
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r.x() = math::polynomial::chebyshev::evaluate(ax, ay, t);
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r.y() = math::polynomial::chebyshev::evaluate(ay, az, t);
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r.z() = math::polynomial::chebyshev::evaluate(az, az + n, t);
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return r;
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}
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} // namespace orbit
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} // namespace physics
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#endif // ANTKEEPER_PHYSICS_ORBIT_TRAJECTORY_HPP
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