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