💿🐜 Antkeeper source code
https://antkeeper.com
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
133 lines
4.3 KiB
133 lines
4.3 KiB
/*
|
|
* 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/astronomy-system.hpp"
|
|
#include "game/astronomy/celestial-coordinates.hpp"
|
|
#include "game/astronomy/celestial-mechanics.hpp"
|
|
#include "game/astronomy/celestial-time.hpp"
|
|
#include "game/astronomy/astronomical-constants.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;
|
|
|
|
astronomy_system::astronomy_system(entt::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),
|
|
ke_tolerance(1e-6),
|
|
ke_iterations(10)
|
|
{}
|
|
|
|
void astronomy_system::update(double t, double dt)
|
|
{
|
|
const double dt_days = dt * days_per_timestep;
|
|
|
|
// Add scaled timestep to current time
|
|
set_universal_time(universal_time + dt_days);
|
|
|
|
// Update horizontal (topocentric) positions of orbiting bodies
|
|
registry.view<orbit_component, transform_component>().each(
|
|
[&](auto entity, auto& orbit, auto& transform)
|
|
{
|
|
ast::orbital_elements orbital_elements;
|
|
orbital_elements.a = orbit.a + orbit.d_a * universal_time;
|
|
orbital_elements.ec = orbit.ec + orbit.d_ec * universal_time;
|
|
orbital_elements.w = orbit.w + orbit.d_w * universal_time;
|
|
orbital_elements.ma = math::wrap_radians(orbit.ma + orbit.d_ma * universal_time);
|
|
orbital_elements.i = orbit.i + orbit.d_i * universal_time;
|
|
orbital_elements.om = math::wrap_radians(orbit.om + orbit.d_om * universal_time);
|
|
|
|
// Calculate ecliptic orbital position
|
|
double3 ecliptic = ast::orbital_elements_to_ecliptic(orbital_elements, ke_tolerance, ke_iterations);
|
|
|
|
// Transform orbital position from ecliptic space to horizontal space
|
|
double3 horizontal = ecliptic_to_horizontal * ecliptic;
|
|
|
|
// Subtract observer's radial distance (planet radius + observer's altitude)
|
|
horizontal.z -= observer_location[0];
|
|
|
|
// Calculate azimuth and elevation
|
|
double3 spherical = ast::rectangular_to_spherical(horizontal);
|
|
double2 az_el = {spherical.z - math::pi<double>, spherical.y};
|
|
|
|
// 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 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::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);
|
|
}
|