/*
* Copyright (C) 2023 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 .
*/
#ifndef ANTKEEPER_GAME_ASTRONOMY_SYSTEM_HPP
#define ANTKEEPER_GAME_ASTRONOMY_SYSTEM_HPP
#include "game/systems/updatable-system.hpp"
#include
#include
#include
#include
#include
#include
#include "game/components/observer-component.hpp"
#include "game/components/atmosphere-component.hpp"
#include "game/components/celestial-body-component.hpp"
#include "game/components/orbit-component.hpp"
#include
/**
* Calculates apparent properties of celestial bodies as seen by an observer.
*/
class astronomy_system:
public updatable_system
{
public:
explicit astronomy_system(entity::registry& registry);
~astronomy_system();
/**
* Adds the timestep `dt`, scaled by set time scale, to the current time, then calculates apparent properties of celestial bodies as seen by an observer.
*
* @param t Time, in seconds.
* @param dt Delta time, in seconds.
*/
virtual void update(float t, float dt);
/**
* Sets the current time.
*
* @param t Time since epoch, in days.
*/
void set_time(double t);
/**
* Sets the factor by which the timestep `dt` will be scaled before being added to the current time.
*
* @param scale Factor by which to scale the timestep.
*/
void set_time_scale(double scale);
/**
* Sets the observer entity.
*
* @param eid Entity ID of the observer.
*/
void set_observer(entity::id eid);
/**
* Sets the number of samples to take when integrating atmospheric transmittance.
*
* @param samples Number of integration samples.
*/
void set_transmittance_samples(std::size_t samples);
void set_sun_light(scene::directional_light* light);
void set_sky_light(scene::ambient_light* light);
void set_moon_light(scene::directional_light* light);
void set_bounce_light(scene::directional_light* light);
void set_bounce_albedo(const double3& albedo);
void set_starlight_illuminance(const double3& illuminance);
void set_sky_pass(::render::sky_pass* pass);
private:
void on_observer_modified(entity::registry& registry, entity::id entity_id);
void on_observer_destroyed(entity::registry& registry, entity::id entity_id);
void on_celestial_body_modified(entity::registry& registry, entity::id entity_id);
void on_celestial_body_destroyed(entity::registry& registry, entity::id entity_id);
void on_orbit_modified(entity::registry& registry, entity::id entity_id);
void on_orbit_destroyed(entity::registry& registry, entity::id entity_id);
void on_atmosphere_modified(entity::registry& registry, entity::id entity_id);
void on_atmosphere_destroyed(entity::registry& registry, entity::id entity_id);
/// Called each time the observer is modified.
void observer_modified();
/// Called each time the celestial body of the reference body is modified.
void reference_body_modified();
/// Called each time the orbit of the reference body is modified.
void reference_orbit_modified();
/// Called each time the atmosphere of the reference body is modified.
void reference_atmosphere_modified();
/// Updates the BCBF to EUS transformation.
void update_bcbf_to_eus(const ::observer_component& observer, const ::celestial_body_component& body);
/// Updates the ICRF to EUS transformation.
void update_icrf_to_eus(const ::celestial_body_component& body, const ::orbit_component& orbit);
/**
* Integrates a transmittance factor due to atmospheric extinction along a ray.
*
* @param ray Ray to cast, in the EUS frame.
* @param samples Number of samples to integrate.
*
* @return Spectral transmittance factor.
*/
double3 integrate_transmittance(const ::observer_component& observer, const ::celestial_body_component& body, const ::atmosphere_component& atmosphere, geom::ray ray) const;
/// Time since epoch, in days.
double time_days;
/// Time since epoch, in centuries.
double time_centuries;
/// Time scale.
double time_scale;
/// Number of transmittance integration samples.
std::size_t transmittance_samples;
/// Entity ID of the observer.
entity::id observer_eid;
/// Entity ID of the reference body.
entity::id reference_body_eid;
/// ENU to EUS transformation.
math::transformation::se3 enu_to_eus;
/// BCBF to EUS transformation.
math::transformation::se3 bcbf_to_eus;
/// ICRF to EUS tranformation.
math::transformation::se3 icrf_to_eus;
scene::directional_light* sun_light;
scene::ambient_light* sky_light;
scene::directional_light* moon_light;
scene::directional_light* bounce_light;
double3 bounce_albedo;
::render::sky_pass* sky_pass;
double3 starlight_illuminance;
};
#endif // ANTKEEPER_GAME_ASTRONOMY_SYSTEM_HPP