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- /*
- * Copyright (C) 2021 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 "ecs/systems/astronomy-system.hpp"
- #include "game/astronomy/celestial-coordinates.hpp"
- #include "game/astronomy/apparent-size.hpp"
- #include "ecs/components/celestial-body-component.hpp"
- #include "ecs/components/transform-component.hpp"
- #include "renderer/passes/sky-pass.hpp"
-
- namespace ecs {
-
- static constexpr double seconds_per_day = 24.0 * 60.0 * 60.0;
-
- astronomy_system::astronomy_system(ecs::registry& registry):
- entity_system(registry),
- universal_time(0.0),
- days_per_timestep(1.0 / seconds_per_day),
- observer_location{0.0, 0.0, 0.0},
- lst(0.0),
- obliquity(0.0),
- sky_pass(nullptr),
- sun(entt::null),
- moon(entt::null)
- {}
-
- void astronomy_system::update(double t, double dt)
- {
- // Add scaled timestep to current time
- set_universal_time(universal_time + dt * days_per_timestep);
-
- // Update horizontal (topocentric) positions of intrasolar celestial bodies
- registry.view<celestial_body_component, transform_component>().each(
- [&](ecs::entity entity, auto& body, auto& transform)
- {
- // Transform orbital position from ecliptic space to horizontal space
- double3 horizontal = ecliptic_to_horizontal * body.orbital_state.r;
-
- // Subtract observer's radial distance (planet radius + observer's altitude)
- horizontal.z -= observer_location[0];
-
- // Convert rectangular horizontal coordinates to spherical
- double3 spherical = ast::rectangular_to_spherical(horizontal);
- spherical.z -= math::pi<double>;
-
- // Find angular radius
- double angular_radius = ast::find_angular_radius(body.radius, spherical.x);
-
- // Transform into local right-handed coordinates
- double3 translation = ast::horizontal_to_right_handed * horizontal;
- double3x3 rotation = ast::horizontal_to_right_handed * ecliptic_to_horizontal;
-
- // Set local transform of transform component
- transform.local.translation = math::type_cast<float>(translation);
- transform.local.rotation = math::type_cast<float>(math::quaternion_cast(rotation));
- transform.local.scale = math::type_cast<float>(double3{body.radius, body.radius, body.radius});
- });
-
- if (sky_pass)
- {
- sky_pass->set_horizon_color({0, 0, 0});
- sky_pass->set_zenith_color({1, 1, 1});
- sky_pass->set_time_of_day(static_cast<float>(universal_time * 60.0 * 60.0));
- //sky_pass->set_observer_location(location[0], location[1], location[2]);
- sky_pass->set_julian_day(static_cast<float>(universal_time));
- }
- }
-
- void astronomy_system::set_universal_time(double time)
- {
- universal_time = time;
- update_axial_rotation();
- }
-
- void astronomy_system::set_time_scale(double scale)
- {
- days_per_timestep = scale / seconds_per_day;
- }
-
- void astronomy_system::set_observer_location(const double3& location)
- {
- observer_location = location;
- update_sidereal_time();
- }
-
- void astronomy_system::set_obliquity(double angle)
- {
- obliquity = angle;
- update_ecliptic_to_horizontal();
- }
-
- void astronomy_system::set_axial_rotation_speed(double speed)
- {
- axial_rotation_speed = speed;
- }
-
- void astronomy_system::set_axial_rotation_at_epoch(double angle)
- {
- axial_rotation_at_epoch = angle;
- update_axial_rotation();
- }
-
- void astronomy_system::set_sky_pass(::sky_pass* pass)
- {
- this->sky_pass = pass;
- }
-
- void astronomy_system::set_sun(ecs::entity entity)
- {
- sun = entity;
- }
-
- void astronomy_system::set_moon(ecs::entity entity)
- {
- moon = entity;
- }
-
- void astronomy_system::update_axial_rotation()
- {
- axial_rotation = math::wrap_radians<double>(axial_rotation_at_epoch + universal_time * axial_rotation_speed);
- update_sidereal_time();
- }
-
- void astronomy_system::update_sidereal_time()
- {
- lst = math::wrap_radians<double>(axial_rotation + observer_location[2]);
- update_ecliptic_to_horizontal();
- }
-
- void astronomy_system::update_ecliptic_to_horizontal()
- {
- ecliptic_to_horizontal = ast::ecliptic_to_horizontal(obliquity, observer_location[1], lst);
- }
-
- } // namespace ecs
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