💿🐜 Antkeeper source code
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275 lines
10 KiB
275 lines
10 KiB
/*
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* Copyright (C) 2021 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 "ecs/systems/astronomy-system.hpp"
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#include "astro/apparent-size.hpp"
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#include "ecs/components/celestial-body-component.hpp"
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#include "ecs/components/transform-component.hpp"
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#include "renderer/passes/sky-pass.hpp"
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#include "color/color.hpp"
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#include "physics/orbit/orbit.hpp"
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#include "physics/time/ut1.hpp"
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#include "geom/cartesian.hpp"
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#include <iostream>
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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(ecs::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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axial_rotation(0.0),
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axial_rotation_at_epoch(0.0),
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axial_rotation_speed(0.0),
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sky_pass(nullptr),
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sun_light(nullptr)
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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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set_universal_time(0.0);
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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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[&](ecs::entity entity, auto& body, auto& transform)
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{
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double time_correction = observer_location[2] / (math::two_pi<double> / 24.0);
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double local_jd = universal_time + time_correction / 24.0 - 0.5;
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double local_time = (local_jd - std::floor(local_jd)) * 24.0;
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double local_lst = local_time / 24.0f * math::two_pi<float>;
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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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double3 horizontal = ecliptic_to_horizontal * double3{1, 0, 0};
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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 Cartesian horizontal coordinates to spherical
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double3 spherical = geom::cartesian::to_spherical(horizontal);
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// Find angular radius
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double angular_radius = astro::find_angular_radius(body.radius, spherical[0]);
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// Transform into local coordinates
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const double3x3 horizontal_to_local = math::rotate_x(-math::half_pi<double>) * math::rotate_z(-math::half_pi<double>);
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double3 translation = horizontal_to_local * horizontal;
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double3x3 rotation = horizontal_to_local * 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::normalize(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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if (sun_light != nullptr)
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{
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const double universal_time_cy = universal_time * 2.7397e-5;
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const double3 solar_system_barycenter = {0, 0, 0};
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physics::orbit::elements<double> earth_elements;
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earth_elements.a = 1.00000261 + 0.00000562 * universal_time_cy;
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earth_elements.e = 0.01671123 + -0.00004392 * universal_time_cy;
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earth_elements.i = math::radians(-0.00001531) + math::radians(-0.01294668) * universal_time_cy;
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earth_elements.raan = 0.0;
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const double earth_elements_mean_longitude = math::radians(100.46457166) + math::radians(35999.37244981) * universal_time_cy;
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const double earth_elements_longitude_perihelion = math::radians(102.93768193) + math::radians(0.32327364) * universal_time_cy;
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earth_elements.w = earth_elements_longitude_perihelion - earth_elements.raan;
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earth_elements.ta = earth_elements_mean_longitude - earth_elements_longitude_perihelion;
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// Calculate semi-minor axis, b
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double b = physics::orbit::derive_semiminor_axis(earth_elements.a, earth_elements.e);
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// Solve Kepler's equation for eccentric anomaly (E)
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double ea = physics::orbit::kepler_ea(earth_elements.e, earth_elements.ta, 10, 1e-6);
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// Calculate radial distance, r; and true anomaly, v
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double xv = earth_elements.a * (std::cos(ea) - earth_elements.e);
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double yv = b * std::sin(ea);
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double r = std::sqrt(xv * xv + yv * yv);
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double ta = std::atan2(yv, xv);
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// Position of the body in perifocal space
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const math::vector3<double> earth_position_pqw = math::quaternion<double>::rotate_z(ta) * math::vector3<double>{r, 0, 0};
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const double earth_axial_tilt = math::radians(23.45);
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const double earth_axial_rotation = physics::time::ut1::era(universal_time);
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const double earth_radius_au = 4.2635e-5;
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const double observer_altitude = earth_radius_au;
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const double observer_latitude = math::radians(0.0);
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const double observer_longitude = math::radians(0.0);
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const physics::frame<double> earth_inertial_to_pqw = physics::orbit::inertial::to_perifocal(solar_system_barycenter, earth_elements.raan, earth_elements.i, earth_elements.w);
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const math::vector3<double> earth_position_inertial = earth_inertial_to_pqw.inverse() * earth_position_pqw;
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const math::vector3<double> sun_position_intertial = math::vector3<double>{0, 0, 0};
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const physics::frame<double> earth_inertial_to_bci = physics::orbit::inertial::to_bci(earth_position_inertial, earth_elements.i, earth_axial_tilt);
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const physics::frame<double> earth_inertial_to_bcbf = physics::orbit::inertial::to_bcbf(earth_position_inertial, earth_elements.i, earth_axial_tilt, earth_axial_rotation);
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const physics::frame<double> earth_bcbf_to_topo = physics::orbit::bcbf::to_topocentric(observer_altitude, observer_latitude, observer_longitude);
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const math::vector3<double> sun_position_earth_bci = earth_inertial_to_bci * sun_position_intertial;
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const math::vector3<double> sun_position_earth_bcbf = earth_inertial_to_bcbf * sun_position_intertial;
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const math::vector3<double> sun_position_earth_topo = earth_bcbf_to_topo * sun_position_earth_bcbf;
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const math::vector3<double> sun_radec = geom::cartesian::to_spherical(sun_position_earth_bci);
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const math::vector3<double> sun_azel = geom::cartesian::to_spherical(sun_position_earth_topo);
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const double sun_az = sun_azel.z;
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const double sun_el = sun_azel.y;
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double sun_ra = sun_radec.z;
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const double sun_dec = sun_radec.y;
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if (sun_ra < 0.0)
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sun_ra += math::two_pi<double>;
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std::cout << "ra: " << (sun_ra / math::two_pi<double> * 24.0) << "; dec: " << math::degrees(sun_dec) << std::endl;
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std::cout << "az: " << math::degrees(math::pi<double> - sun_az) << "; el: " << math::degrees(sun_el) << std::endl;
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float az = spherical.z;
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float el = spherical.y;
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if (az < 0.0f)
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az += math::two_pi<float>;
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//std::cout << "local: " << translation << std::endl;
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//std::cout << "az: " << math::degrees(az) << "; ";
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//std::cout << "el: " << math::degrees(el) << std::endl;
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math::quaternion<float> sun_azimuth_rotation = math::angle_axis(static_cast<float>(spherical.z), float3{0, 1, 0});
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math::quaternion<float> sun_elevation_rotation = math::angle_axis(static_cast<float>(spherical.y), float3{1, 0, 0});
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math::quaternion<float> sun_az_el_rotation = math::normalize(sun_azimuth_rotation * sun_elevation_rotation);
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// Set sun color
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float cct = 3000.0f + std::sin(spherical.y) * 5000.0f;
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float3 color_xyz = color::cct::to_xyz(cct);
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float3 color_acescg = color::xyz::to_acescg(color_xyz);
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sun_light->set_color(color_acescg);
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// Set sun intensity (in lux)
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float intensity = std::max(0.0, std::sin(spherical.y) * 108000.0f);
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sun_light->set_intensity(intensity);
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//sun_light->set_translation({0, 500, 0});
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sun_light->set_translation(transform.local.translation);
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//sun_light->set_rotation(transform.local.rotation);
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//sun_light->set_rotation(sun_az_el_rotation);
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//sun_light->set_rotation(sun_elevation_rotation);
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sun_light->set_rotation(math::look_rotation(math::normalize(-transform.local.translation), {0, 0, -1}));
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if (this->sky_pass)
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{
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this->sky_pass->set_sun_coordinates(transform.local.rotation * float3{0, 0, -1}, {static_cast<float>(spherical.z), static_cast<float>(spherical.y)});
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}
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}
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});
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if (sky_pass)
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{
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// Calculate local time
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double time_correction = observer_location[2] / (math::two_pi<double> / 24.0);
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double local_jd = universal_time + time_correction / 24.0 - 0.5;
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double local_time = (local_jd - std::floor(local_jd)) * 24.0;
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sky_pass->set_time_of_day(local_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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update_axial_rotation();
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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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sky_pass = pass;
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}
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void astronomy_system::set_sun_light(scene::directional_light* light)
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{
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sun_light = light;
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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 = coordinates::rectangular::ecliptic::to_horizontal(obliquity, observer_location[1], lst);
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}
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} // namespace ecs
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