💿🐜 Antkeeper source code
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201 lines
5.2 KiB
201 lines
5.2 KiB
/*
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* Copyright (C) 2023 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_SPRING_HPP
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#define ANTKEEPER_PHYSICS_SPRING_HPP
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#include <engine/math/numbers.hpp>
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#include <engine/physics/frequency.hpp>
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namespace physics {
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/**
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* Solves a numeric spring using the implicit Euler method.
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*
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* @tparam T Value type.
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* @tparam S Scalar type.
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*
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* @param[in,out] x Current value of the spring.
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* @param[in,out] v Current velocity of the spring.
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* @param[in] xt Target value of the spring.
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* @param[in] z Damping ratio of the spring, which can be undamped (`0`), underdamped (`< 1`), critically damped (`1`), or overdamped (`> 1`).
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* @param[in] w Angular frequency of the spring oscillation, in radians per second.
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* @param[in] dt Delta time, in seconds.
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*/
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template <class T, class S>
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constexpr void solve_spring(T& x, T& v, const T& xt, S z, S w, S dt) noexcept
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{
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const auto ww_dt = w * w * dt;
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const auto ww_dtdt = ww_dt * dt;
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const auto f = z * w * dt * S{2} + S{1};
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const auto inv_det = S{1} / (f + ww_dtdt);
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x = (x * f + v * dt + xt * ww_dtdt) * inv_det;
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v = (v + (xt - x) * ww_dt) * inv_det;
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}
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/**
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* Numeric spring.
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*
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* @tparam T Value type.
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* @tparam S Scalar type.
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*/
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template <class T, class S>
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class numeric_spring
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{
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public:
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/// Value type.
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using value_type = T;
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/// Scalar type.
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using scalar_type = S;
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/**
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* Solves the spring using the implicit Euler method.
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*
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* @param dt Delta time, in seconds.
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*/
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inline constexpr void solve(scalar_type dt) noexcept
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{
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solve_spring(m_value, m_velocity, m_target_value, m_damping_ratio, m_angular_frequency, dt);
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}
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/**
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* Sets the current value of the spring.
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*
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* @param value Current value.
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*/
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inline constexpr void set_value(const value_type& value) noexcept
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{
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m_value = value;
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}
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/**
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* Sets the target value of the spring.
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*
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* @param value Target value.
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*/
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inline constexpr void set_target_value(const value_type& value) noexcept
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{
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m_target_value = value;
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}
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/**
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* Sets the velocity of the spring.
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*
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* @param velocity Spring velocity.
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*/
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inline constexpr void set_velocity(const value_type& velocity) noexcept
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{
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m_velocity = velocity;
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}
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/**
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* Sets the damping ratio of the spring.
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*
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* @param ratio Damping ratio, which can be undamped (`0`), underdamped (`< 1`), critically damped (`1`), or overdamped (`> 1`).
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*/
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inline constexpr void set_damping_ratio(scalar_type ratio) noexcept
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{
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m_damping_ratio = ratio;
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}
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/**
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* Sets the angular frequency of the spring oscillation.
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*
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* @param w Angular frequency, in radians per second.
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*/
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inline constexpr void set_angular_frequency(scalar_type angular_frequency) noexcept
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{
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m_angular_frequency = angular_frequency;
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}
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/**
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* Sets the oscillation period of the spring.
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*
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* @param period Oscillation period, in seconds.
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*/
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inline constexpr void set_period(scalar_type period) noexcept
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{
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m_angular_frequency = s_to_rads(period);
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}
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/**
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* Sets the oscillation frequency of the spring.
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*
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* @param frequency Oscillation frequency, in hertz.
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*/
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inline constexpr void set_frequency(scalar_type frequency) noexcept
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{
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m_angular_frequency = hz_to_rads(frequency);
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}
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/// Returns the current value of the spring.
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[[nodiscard]] inline constexpr const value_type& get_value() const noexcept
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{
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return m_value;
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}
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/// Returns the target value of the spring.
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[[nodiscard]] inline constexpr const value_type& get_target_value() const noexcept
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{
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return m_target_value;
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}
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/// Returns the velocity of the spring.
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[[nodiscard]] inline constexpr const value_type& get_velocity() const noexcept
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{
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return m_velocity;
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}
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/// Returns the damping ratio of the spring.
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[[nodiscard]] inline constexpr scalar_type get_damping_ratio() const noexcept
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{
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return m_damping_ratio;
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}
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/// Returns the angular frequency of the spring oscillation, in radians per second.
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[[nodiscard]] inline constexpr scalar_type get_angular_frequency() const noexcept
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{
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return m_angular_frequency;
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}
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/// Returns the oscillation period of the spring, in seconds.
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[[nodiscard]] inline constexpr scalar_type get_period() const noexcept
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{
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return rads_to_s(m_angular_frequency);
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}
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/// Returns the oscillation frequency of the spring, in hertz.
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[[nodiscard]] inline constexpr scalar_type get_frequency() const noexcept
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{
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return rads_to_hz(m_angular_frequency);
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}
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private:
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value_type m_value{};
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value_type m_target_value{};
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value_type m_velocity{};
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scalar_type m_damping_ratio{1};
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scalar_type m_angular_frequency{math::two_pi<scalar_type>};
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};
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} // namespace physics
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#endif // ANTKEEPER_PHYSICS_SPRING_HPP
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