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- /*
- * Copyright (C) 2020 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/>.
- */
-
- #include "game/systems/solar-system.hpp"
- #include "game/astronomy/celestial-coordinates.hpp"
- #include "game/astronomy/celestial-mechanics.hpp"
- #include "game/astronomy/celestial-time.hpp"
- #include "game/components/orbit-component.hpp"
- #include "game/components/transform-component.hpp"
-
- using namespace ecs;
-
- static constexpr double seconds_per_day = 24.0 * 60.0 * 60.0;
-
- solar_system::solar_system(entt::registry& registry):
- entity_system(registry),
- julian_date(0.0),
- time_scale(1.0),
- latitude(0.0),
- longitude(0.0),
- altitude(0.0)
- {}
-
- void solar_system::update(double t, double dt)
- {
- // Add scaled timestep to Julian date
- set_julian_date(julian_date + (dt * time_scale) / seconds_per_day);
-
- // Update horizontal (topocentric) positions of orbiting bodies
- registry.view<orbit_component, transform_component>().each(
- [&](auto entity, auto& orbit, auto& transform)
- {
- double a = orbit.a;
- double ec = orbit.ec;
- double w = orbit.w;
- double ma = orbit.ma;
- double i = orbit.i;
- double om = orbit.om;
-
- double3 ecliptic = ast::solve_kepler(a, ec, w, ma, i, om);
- double3 horizontal = ecliptic_to_horizontal * ecliptic;
-
- // Subtract Earth's radius (in AU), for positon of observer
- horizontal.z -= 4.25875e-5;
-
- // Transform into local right-handed coordinates
- double3 translation = ast::horizontal_to_right_handed * horizontal;
- double3x3 rotation = ast::horizontal_to_right_handed * ecliptic_to_horizontal;
-
- transform.local.translation = math::type_cast<float>(translation);
- transform.local.rotation = math::type_cast<float>(math::quaternion_cast(rotation));
- });
- }
-
- void solar_system::set_julian_date(double jd)
- {
- julian_date = jd;
-
- // Recalculate obliquity of the ecliptic
- ecl = ast::approx_ecliptic_obliquity(julian_date);
-
- // Recalculate LMST
- lmst = ast::jd_to_lmst(julian_date, longitude);
-
- // Recalculate ecliptic to horizontal transformation matrix
- ecliptic_to_horizontal = ast::ecliptic_to_horizontal(ecl, latitude, lmst);
- }
-
- void solar_system::set_time_scale(double scale)
- {
- time_scale = scale;
- }
-
- void solar_system::set_observer_location(double latitude, double longitude, double altitude)
- {
- this->latitude = latitude;
- this->longitude = longitude;
- this->altitude = altitude;
-
- // Recalculate LMST
- lmst = ast::jd_to_lmst(julian_date, longitude);
-
- // Recalculate ecliptic to horizontal transformation matrix
- ecliptic_to_horizontal = ast::ecliptic_to_horizontal(ecl, latitude, lmst);
- }
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