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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/>.
- */
-
- #ifndef ANTKEEPER_ECS_ASTRONOMY_SYSTEM_HPP
- #define ANTKEEPER_ECS_ASTRONOMY_SYSTEM_HPP
-
- #include "entity-system.hpp"
- #include "ecs/entity.hpp"
- #include "utility/fundamental-types.hpp"
-
- namespace ecs {
-
- /**
- * Calculates apparent properties of celestial bodies relative to an observer (magnitude, angular radius, horizontal coordinates) and modifies their model component and/or light component to render them accordingly.
- */
- class astronomy_system:
- public entity_system
- {
- public:
- astronomy_system(ecs::registry& registry);
-
- /**
- * Scales then adds the timestep `dt` to the current time, then recalculates the positions of celestial bodies.
- *
- * @param t Time, in seconds.
- * @param dt Delta time, in seconds.
- */
- virtual void update(double t, double dt);
-
- /**
- * Sets the current universal time.
- *
- * @param time Universal time, in days.
- */
- void set_universal_time(double time);
-
- /**
- * Sets the factor by which the timestep `dt` will be scaled before being added to the current universal time.
- *
- * @param scale Factor by which to scale the timestep.
- */
- void set_time_scale(double scale);
-
- /**
- * Sets the location of the observer.
- *
- * @param location Spherical coordinates of the observer, in the ISO order of radial distance, polar angle (radians), and azimuthal angle (radians).
- */
- void set_observer_location(const double3& location);
-
- /**
- * Sets the obliquity of the ecliptic, a.k.a. axial tilt.
- *
- * @param angle Angle between the planet's rotational axis and its orbital axis, in radians.
- */
- void set_obliquity(double angle);
-
- /**
- * Sets the rotational speed of the observer's planet.
- *
- * @param speed Rotational speed, in radians per day.
- */
- void set_axial_rotation_speed(double speed);
-
- /**
- * Sets the axial rotation of the observer's planet when the universal time is `0.0`.
- *
- * @param angle Axial rotation angle, in radians.
- */
- void set_axial_rotation_at_epoch(double angle);
-
- private:
- /// Updates the axial rotation angle
- void update_axial_rotation();
-
- /// Updates the local sidereal time (LST) and dependent variables
- void update_sidereal_time();
-
- /// Updates the ecliptic-to-horizontal transformation matrix
- void update_ecliptic_to_horizontal();
-
- double universal_time;
- double days_per_timestep;
- double lst;
- double axial_rotation_at_epoch;
- double axial_rotation_speed;
- double axial_rotation;
- double3 observer_location;
- double obliquity;
- double3x3 ecliptic_to_horizontal;
- };
-
- } // namespace ecs
-
- #endif // ANTKEEPER_ECS_ASTRONOMY_SYSTEM_HPP
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