💿🐜 Antkeeper source code
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132 lines
4.3 KiB
132 lines
4.3 KiB
/*
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* Copyright (C) 2020 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 "game/systems/solar-system.hpp"
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#include "game/astronomy/celestial-coordinates.hpp"
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#include "game/astronomy/celestial-mechanics.hpp"
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#include "game/astronomy/celestial-time.hpp"
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#include "game/components/orbit-component.hpp"
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#include "game/components/transform-component.hpp"
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#include <iostream>
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using namespace ecs;
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static constexpr double seconds_per_day = 24.0 * 60.0 * 60.0;
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solar_system::solar_system(entt::registry& registry):
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entity_system(registry),
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julian_date(0.0),
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time_scale(1.0),
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latitude(0.0),
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longitude(0.0),
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altitude(0.0)
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{}
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void solar_system::update(double t, double dt)
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{
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// Add scaled timestep to Julian date
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set_julian_date(julian_date + (dt * time_scale) / seconds_per_day);
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const double ke_tolerance = 1e-6;
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const std::size_t ke_iterations = 10;
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ast::orbital_elements sun_elements;
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sun_elements.a = 1.0;
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sun_elements.ec = 0.016709;
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sun_elements.w = math::radians(282.9404);
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sun_elements.ma = math::radians(356.0470);
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sun_elements.i = math::radians(0.0);
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sun_elements.om = math::radians(0.0);
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const double j2k_day = julian_date - 2451545.0;
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const double j2k_century = (julian_date - 2451545.0) / 36525.0;
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sun_elements.ec += math::radians(-1.151e-9) * j2k_day;
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sun_elements.w += math::radians(4.70935e-5) * j2k_day;
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sun_elements.ma += math::radians(0.9856002585) * j2k_day;
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ast::orbital_state sun_ecliptic = ast::orbital_elements_to_state(sun_elements, ke_tolerance, ke_iterations);
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double3 sun_horizontal = ecliptic_to_horizontal * sun_ecliptic.r;
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sun_horizontal.z -= 4.25875e-5;
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double3 sun_spherical = ast::rectangular_to_spherical(sun_horizontal);
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double2 sun_az_el = {sun_spherical.z - math::pi<double>, sun_spherical.y};
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//std::cout << "new azel: " << math::degrees(sun_az_el.x) << ", " << math::degrees(sun_az_el.y) << std::endl;
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// Update horizontal (topocentric) positions of orbiting bodies
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registry.view<orbit_component, transform_component>().each(
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[&](auto entity, auto& orbit, auto& transform)
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{
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/*
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double a = orbit.a;
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double ec = orbit.ec;
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double w = orbit.w;
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double ma = orbit.ma;
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double i = orbit.i;
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double om = orbit.om;
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double3 ecliptic = ast::solve_kepler(a, ec, w, ma, i, om);
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double3 horizontal = ecliptic_to_horizontal * ecliptic;
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// Subtract Earth's radius (in AU), for positon of observer
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horizontal.z -= 4.25875e-5;
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// Transform into local right-handed coordinates
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double3 translation = ast::horizontal_to_right_handed * horizontal;
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double3x3 rotation = ast::horizontal_to_right_handed * ecliptic_to_horizontal;
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transform.local.translation = math::type_cast<float>(translation);
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transform.local.rotation = math::type_cast<float>(math::quaternion_cast(rotation));
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*/
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});
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}
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void solar_system::set_julian_date(double jd)
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{
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julian_date = jd;
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// Recalculate obliquity of the ecliptic
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ecl = ast::approx_ecliptic_obliquity(julian_date);
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// Recalculate LMST
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lmst = ast::jd_to_lmst(julian_date, longitude);
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// Recalculate ecliptic to horizontal transformation matrix
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ecliptic_to_horizontal = ast::ecliptic_to_horizontal(ecl, latitude, lmst);
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}
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void solar_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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void solar_system::set_observer_location(double latitude, double longitude, double altitude)
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{
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this->latitude = latitude;
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this->longitude = longitude;
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this->altitude = altitude;
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// Recalculate LMST
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lmst = ast::jd_to_lmst(julian_date, longitude);
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// Recalculate ecliptic to horizontal transformation matrix
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ecliptic_to_horizontal = ast::ecliptic_to_horizontal(ecl, latitude, lmst);
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}
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