💿🐜 Antkeeper source code
https://antkeeper.com
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91 lines
3.0 KiB
91 lines
3.0 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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#include "ecs/systems/orbit-system.hpp"
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#include "ecs/components/orbit-component.hpp"
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#include "ecs/entity.hpp"
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#include "physics/orbit/orbit.hpp"
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namespace ecs {
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orbit_system::orbit_system(ecs::registry& registry):
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entity_system(registry),
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universal_time(0.0),
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time_scale(1.0),
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ke_iterations(10),
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ke_tolerance(1e-6)
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{}
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void orbit_system::update(double t, double dt)
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{
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// Add scaled timestep to current time
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set_universal_time(universal_time + dt * time_scale);
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// Update the orbital state of orbiting bodies
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registry.view<orbit_component>().each(
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[&](ecs::entity entity, auto& orbit)
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{
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// Calculate semi-minor axis (b)
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const double b = physics::orbit::derive_semiminor_axis(orbit.elements.a, orbit.elements.e);
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// Solve Kepler's equation for eccentric anomaly (E)
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const double ea = physics::orbit::kepler_ea(orbit.elements.e, orbit.elements.ta, ke_iterations, ke_tolerance);
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// Calculate radial distance and true anomaly (nu)
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const double xv = orbit.elements.a * (std::cos(ea) - orbit.elements.e);
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const double yv = b * std::sin(ea);
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const double distance = std::sqrt(xv * xv + yv * yv);
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const double ta = std::atan2(yv, xv);
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// Calculate Cartesian position (r) in perifocal space
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const math::vector3<double> r_perifocal = math::quaternion<double>::rotate_z(ta) * math::vector3<double>{distance, 0, 0};
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/// @TODO Calculate Cartesian velocity (v) in perifocal space
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//const math::vector3<double> v_perifocal = ...
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// Construct perifocal to inertial reference frame
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const physics::frame<double> perifocal_to_inertial = physics::orbit::inertial::to_perifocal
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(
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{0, 0, 0},
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orbit.elements.raan,
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orbit.elements.i,
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orbit.elements.w
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).inverse();
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// Transform orbital state vectors from perifocal space to the parent inertial space
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const math::vector3<double> r_inertial = perifocal_to_inertial.transform(r_perifocal);
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//const math::vector3<double> v_inertial = perifocal_frame.transform(v_perifocal);
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// Update orbital state of component
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orbit.state.r = r_inertial;
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//orbit.state.v = v_inertial;
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});
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}
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void orbit_system::set_universal_time(double time)
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{
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universal_time = time;
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}
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void orbit_system::set_time_scale(double scale)
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{
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time_scale = scale;
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}
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} // namespace ecs
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