💿🐜 Antkeeper source code
https://antkeeper.com
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628 lines
24 KiB
628 lines
24 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 "game/system/astronomy.hpp"
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#include "astro/apparent-size.hpp"
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#include "game/component/blackbody.hpp"
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#include "game/component/transform.hpp"
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#include "game/component/diffuse-reflector.hpp"
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#include "geom/intersection.hpp"
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#include "geom/cartesian.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 "physics/time/jd.hpp"
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#include "physics/light/photometry.hpp"
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#include "physics/light/luminosity.hpp"
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#include "physics/light/refraction.hpp"
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#include "physics/gas/atmosphere.hpp"
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#include "geom/cartesian.hpp"
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#include "astro/apparent-size.hpp"
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#include "geom/solid-angle.hpp"
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#include "math/polynomial.hpp"
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#include <iostream>
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namespace game {
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namespace system {
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astronomy::astronomy(entity::registry& registry):
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updatable(registry),
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time_days(0.0),
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time_centuries(0.0),
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time_scale(1.0),
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observer_eid(entt::null),
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reference_body_eid(entt::null),
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transmittance_samples(0),
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sun_light(nullptr),
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sky_light(nullptr),
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moon_light(nullptr),
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bounce_light(nullptr),
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bounce_albedo{0, 0, 0},
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sky_pass(nullptr),
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starlight_illuminance{0, 0, 0}
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{
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// Construct ENU to EUS transformation
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enu_to_eus = math::transformation::se3<double>
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{
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{0, 0, 0},
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math::quaternion<double>::rotate_x(-math::half_pi<double>)
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};
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registry.on_construct<game::component::observer>().connect<&astronomy::on_observer_modified>(this);
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registry.on_update<game::component::observer>().connect<&astronomy::on_observer_modified>(this);
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registry.on_destroy<game::component::observer>().connect<&astronomy::on_observer_destroyed>(this);
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registry.on_construct<game::component::celestial_body>().connect<&astronomy::on_celestial_body_modified>(this);
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registry.on_update<game::component::celestial_body>().connect<&astronomy::on_celestial_body_modified>(this);
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registry.on_destroy<game::component::celestial_body>().connect<&astronomy::on_celestial_body_destroyed>(this);
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registry.on_construct<game::component::orbit>().connect<&astronomy::on_orbit_modified>(this);
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registry.on_update<game::component::orbit>().connect<&astronomy::on_orbit_modified>(this);
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registry.on_destroy<game::component::orbit>().connect<&astronomy::on_orbit_destroyed>(this);
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registry.on_construct<game::component::atmosphere>().connect<&astronomy::on_atmosphere_modified>(this);
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registry.on_update<game::component::atmosphere>().connect<&astronomy::on_atmosphere_modified>(this);
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registry.on_destroy<game::component::atmosphere>().connect<&astronomy::on_atmosphere_destroyed>(this);
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}
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astronomy::~astronomy()
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{
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registry.on_construct<game::component::observer>().disconnect<&astronomy::on_observer_modified>(this);
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registry.on_update<game::component::observer>().disconnect<&astronomy::on_observer_modified>(this);
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registry.on_destroy<game::component::observer>().disconnect<&astronomy::on_observer_destroyed>(this);
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registry.on_construct<game::component::celestial_body>().disconnect<&astronomy::on_celestial_body_modified>(this);
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registry.on_update<game::component::celestial_body>().disconnect<&astronomy::on_celestial_body_modified>(this);
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registry.on_destroy<game::component::celestial_body>().disconnect<&astronomy::on_celestial_body_destroyed>(this);
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registry.on_construct<game::component::orbit>().disconnect<&astronomy::on_orbit_modified>(this);
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registry.on_update<game::component::orbit>().disconnect<&astronomy::on_orbit_modified>(this);
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registry.on_destroy<game::component::orbit>().disconnect<&astronomy::on_orbit_destroyed>(this);
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registry.on_construct<game::component::atmosphere>().disconnect<&astronomy::on_atmosphere_modified>(this);
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registry.on_update<game::component::atmosphere>().disconnect<&astronomy::on_atmosphere_modified>(this);
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registry.on_destroy<game::component::atmosphere>().disconnect<&astronomy::on_atmosphere_destroyed>(this);
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}
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void astronomy::update(double t, double dt)
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{
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double3 sky_light_illuminance = {0.0, 0.0, 0.0};
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// Add scaled timestep to current time
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set_time(time_days + dt * time_scale);
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// Abort if no valid observer entity or reference body entity
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if (observer_eid == entt::null || reference_body_eid == entt::null)
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return;
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// Get pointer to observer component
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const auto observer = registry.try_get<component::observer>(observer_eid);
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// Abort if no observer component
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if (!observer)
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return;
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// Get pointers to reference body components
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const auto
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[
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reference_body,
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reference_orbit,
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reference_atmosphere
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] = registry.try_get<component::celestial_body, component::orbit, component::atmosphere>(reference_body_eid);
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// Abort if no reference body or reference orbit
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if (!reference_body || !reference_orbit)
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return;
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// Update ICRF to EUS transformation
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update_icrf_to_eus(*reference_body, *reference_orbit);
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// Set the transform component translations of orbiting bodies to their topocentric positions
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registry.view<component::celestial_body, component::orbit, component::transform>().each(
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[&](entity::id entity_id, const auto& body, const auto& orbit, auto& transform)
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{
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// Skip reference body entity
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if (entity_id == reference_body_eid)
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return;
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// Transform orbital Cartesian position (r) from the ICRF frame to the EUS frame
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const double3 r_eus = icrf_to_eus * orbit.position;
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// Evaluate body orientation polynomials
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const double body_pole_ra = math::polynomial::horner(body.pole_ra.begin(), body.pole_ra.end(), time_centuries);
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const double body_pole_dec = math::polynomial::horner(body.pole_dec.begin(), body.pole_dec.end(), time_centuries);
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const double body_prime_meridian = math::polynomial::horner(body.prime_meridian.begin(), body.prime_meridian.end(), time_days);
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// Determine body orientation in the ICRF frame
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math::quaternion<double> rotation_icrf = physics::orbit::frame::bcbf::to_bci
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(
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body_pole_ra,
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body_pole_dec,
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body_prime_meridian
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).r;
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// Transform body orientation from the ICRF frame to the EUS frame.
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math::quaternion<double> rotation_eus = math::normalize(icrf_to_eus.r * rotation_icrf);
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// Update local transform
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if (orbit.parent != entt::null)
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{
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transform.local.translation = math::normalize(float3(r_eus));
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transform.local.rotation = math::quaternion<float>(rotation_eus);
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transform.local.scale = {1.0f, 1.0f, 1.0f};
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}
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});
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constexpr double3 bounce_normal = {0, 1, 0};
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double3 bounce_illuminance = {0, 0, 0};
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// Update blackbody lighting
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registry.view<component::celestial_body, component::orbit, component::blackbody>().each(
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[&, bounce_normal](entity::id entity_id, const auto& blackbody_body, const auto& blackbody_orbit, const auto& blackbody)
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{
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// Transform blackbody position from ICRF frame to EUS frame
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const double3 blackbody_position_eus = icrf_to_eus * blackbody_orbit.position;
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// Measure distance and direction, in EUS frame, from observer to blackbody
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const double observer_blackbody_distance = math::length(blackbody_position_eus);
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const double3 observer_blackbody_direction_eus = blackbody_position_eus / observer_blackbody_distance;
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// Measure blackbody solid angle as seen by observer
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const double observer_blackbody_angular_radius = astro::angular_radius(blackbody_body.radius, observer_blackbody_distance);
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const double observer_blackbody_solid_angle = geom::solid_angle::cone(observer_blackbody_angular_radius);
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// Calculate illuminance from blackbody reaching observer
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const double3 observer_blackbody_illuminance = blackbody.luminance * observer_blackbody_solid_angle;
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// Calculate illuminance from blackbody reaching observer after atmospheric extinction
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double3 observer_blackbody_transmitted_illuminance = observer_blackbody_illuminance;
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if (reference_atmosphere)
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{
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// Construct ray at observer pointing towards the blackbody
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const geom::ray<double> ray = {{0, 0, 0}, observer_blackbody_direction_eus};
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// Integrate atmospheric spectral transmittance factor between observer and blackbody
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const double3 transmittance = integrate_transmittance(*observer, *reference_body, *reference_atmosphere, ray);
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// Attenuate illuminance from blackbody reaching observer by spectral transmittance factor
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observer_blackbody_transmitted_illuminance *= transmittance;
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}
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// Update sun light
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if (sun_light != nullptr)
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{
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const double3 blackbody_up_eus = icrf_to_eus.r * double3{0, 0, 1};
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sun_light->set_rotation
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(
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math::look_rotation
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(
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float3(-observer_blackbody_direction_eus),
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float3(blackbody_up_eus)
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)
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);
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sun_light->set_color(float3(observer_blackbody_transmitted_illuminance));
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// Bounce sun light
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bounce_illuminance += std::max(0.0, math::dot(bounce_normal, -observer_blackbody_direction_eus)) * observer_blackbody_transmitted_illuminance * bounce_albedo;
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}
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// Update sky light
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if (sky_light != nullptr)
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{
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// Calculate sky illuminance
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double3 blackbody_position_enu_spherical = physics::orbit::frame::enu::spherical(enu_to_eus.inverse() * blackbody_position_eus);
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const double sky_illuminance = 25000.0 * std::max<double>(0.0, std::sin(blackbody_position_enu_spherical.y()));
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// Add sky illuminance to sky light illuminance
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sky_light_illuminance += {sky_illuminance, sky_illuminance, sky_illuminance};
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// Add starlight illuminance to sky light illuminance
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sky_light_illuminance += starlight_illuminance;
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// Update sky light
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sky_light->set_color(float3(sky_light_illuminance));
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// Bounce sky light
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bounce_illuminance += sky_light_illuminance * bounce_albedo;
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}
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// Upload blackbody params to sky pass
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if (this->sky_pass)
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{
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this->sky_pass->set_sun_position(float3(blackbody_position_eus));
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this->sky_pass->set_sun_luminance(float3(blackbody.luminance));
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this->sky_pass->set_sun_illuminance(float3(observer_blackbody_illuminance), float3(observer_blackbody_transmitted_illuminance));
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this->sky_pass->set_sun_angular_radius(static_cast<float>(observer_blackbody_angular_radius));
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}
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// Update diffuse reflectors
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this->registry.view<component::celestial_body, component::orbit, component::diffuse_reflector, component::transform>().each(
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[&, bounce_normal](entity::id entity_id, const auto& reflector_body, const auto& reflector_orbit, const auto& reflector, const auto& transform)
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{
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// Transform reflector position from ICRF frame to EUS frame
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const double3 reflector_position_eus = icrf_to_eus * reflector_orbit.position;
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// Measure distance and direction, in EUS frame, from observer to reflector
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const double observer_reflector_distance = math::length(reflector_position_eus);
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const double3 observer_reflector_direction_eus = reflector_position_eus / observer_reflector_distance;
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// Measure distance and direction, in EUS frame, from reflector to blackbody
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double3 reflector_blackbody_direction_eus = blackbody_position_eus - reflector_position_eus;
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const double reflector_blackbody_distance = math::length(reflector_blackbody_direction_eus);
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reflector_blackbody_direction_eus /= reflector_blackbody_distance;
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// Measure blackbody solid angle as seen by reflector
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const double reflector_blackbody_angular_radius = astro::angular_radius(blackbody_body.radius, reflector_blackbody_distance);
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const double reflector_blackbody_solid_angle = geom::solid_angle::cone(reflector_blackbody_angular_radius);
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// Calculate blackbody illuminance reaching reflector
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const double3 reflector_blackbody_illuminance = blackbody.luminance * reflector_blackbody_solid_angle;
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// Measure reflector solid angle as seen by observer
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const double observer_reflector_angular_radius = astro::angular_radius(reflector_body.radius, observer_reflector_distance);
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const double observer_reflector_solid_angle = geom::solid_angle::cone(observer_reflector_angular_radius);
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// Determine phase factor of reflector as seen by observer
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const double observer_reflector_phase_factor = dot(observer_reflector_direction_eus, -reflector_blackbody_direction_eus) * 0.5 + 0.5;
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// Measure observer reference body solid angle as seen by reflector
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const double reflector_observer_angular_radius = astro::angular_radius(reference_body->radius, observer_reflector_distance);
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const double reflector_observer_solid_angle = geom::solid_angle::cone(reflector_observer_angular_radius);
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// Determine phase factor of observer reference body as by reflector
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const double reflector_observer_phase_factor = dot(-observer_reflector_direction_eus, -observer_blackbody_direction_eus) * 0.5 + 0.5;
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// Calculate spectral transmittance between observer and reflector factor due to atmospheric extinction
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double3 observer_reflector_transmittance = {1, 1, 1};
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if (reference_atmosphere)
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{
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const geom::ray<double> ray = {{0, 0, 0}, observer_reflector_direction_eus};
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observer_reflector_transmittance = integrate_transmittance(*observer, *reference_body, *reference_atmosphere, ray);
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}
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// Measure luminance of observer reference body as seen by reflector
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const double3 reflector_observer_luminance = observer_blackbody_illuminance * reference_body->albedo * observer_reflector_transmittance * reflector_observer_phase_factor * math::inverse_pi<double>;
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// Measure illuminance from observer reference body reaching reflector
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const double3 reflector_observer_illuminance = reflector_observer_luminance * reflector_observer_solid_angle;
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// Measure luminance of reflector as seen by observer
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const double3 observer_reflector_luminance = (reflector_blackbody_illuminance * observer_reflector_phase_factor + reflector_observer_illuminance) * reflector.albedo * observer_reflector_transmittance * math::inverse_pi<double>;
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// Measure illuminance from reflector reaching observer
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const double3 observer_reflector_illuminance = observer_reflector_luminance * observer_reflector_solid_angle;
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if (this->sky_pass)
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{
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this->sky_pass->set_moon_position(transform.local.translation);
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this->sky_pass->set_moon_rotation(transform.local.rotation);
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this->sky_pass->set_moon_angular_radius(static_cast<float>(observer_reflector_angular_radius));
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this->sky_pass->set_moon_sunlight_direction(float3(-reflector_blackbody_direction_eus));
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this->sky_pass->set_moon_sunlight_illuminance(float3(reflector_blackbody_illuminance * observer_reflector_transmittance));
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this->sky_pass->set_moon_planetlight_direction(float3(observer_reflector_direction_eus));
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this->sky_pass->set_moon_planetlight_illuminance(float3(reflector_observer_illuminance * observer_reflector_transmittance));
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this->sky_pass->set_moon_illuminance(float3(observer_reflector_illuminance / observer_reflector_transmittance), float3(observer_reflector_illuminance));
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}
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if (this->moon_light)
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{
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const float3 reflector_up_eus = float3(icrf_to_eus.r * double3{0, 0, 1});
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this->moon_light->set_color(float3(observer_reflector_illuminance));
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this->moon_light->set_rotation
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(
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math::look_rotation
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(
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float3(-observer_reflector_direction_eus),
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reflector_up_eus
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)
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);
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// Bounce moon light
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bounce_illuminance += std::max(0.0, math::dot(bounce_normal, -observer_reflector_direction_eus)) * observer_reflector_illuminance * bounce_albedo;
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}
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});
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});
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if (bounce_light)
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{
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bounce_light->set_color(float3(bounce_illuminance));
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}
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}
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void astronomy::set_time(double t)
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{
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time_days = t;
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time_centuries = time_days * physics::time::jd::centuries_per_day<double>;
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}
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void astronomy::set_time_scale(double scale)
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{
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time_scale = scale;
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}
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void astronomy::set_observer(entity::id eid)
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{
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if (observer_eid != eid)
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{
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observer_eid = eid;
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if (observer_eid != entt::null)
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observer_modified();
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else
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reference_body_eid = entt::null;
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}
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}
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void astronomy::set_transmittance_samples(std::size_t samples)
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{
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transmittance_samples = samples;
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}
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void astronomy::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::set_sky_light(scene::ambient_light* light)
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{
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sky_light = light;
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}
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void astronomy::set_moon_light(scene::directional_light* light)
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{
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moon_light = light;
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}
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void astronomy::set_bounce_light(scene::directional_light* light)
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{
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bounce_light = light;
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}
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void astronomy::set_bounce_albedo(const double3& albedo)
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{
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bounce_albedo = albedo;
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}
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void astronomy::set_starlight_illuminance(const double3& illuminance)
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{
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starlight_illuminance = illuminance;
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}
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void astronomy::set_sky_pass(::render::sky_pass* pass)
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{
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this->sky_pass = pass;
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if (sky_pass)
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{
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if (observer_eid != entt::null)
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{
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// Get pointer to observer
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const auto observer = registry.try_get<component::observer>(reference_body_eid);
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sky_pass->set_observer_elevation(static_cast<float>(observer->elevation));
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}
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if (reference_body_eid != entt::null)
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{
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// Get pointer to reference celestial body
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const auto reference_body = registry.try_get<component::celestial_body>(reference_body_eid);
|
|
|
|
if (reference_body)
|
|
sky_pass->set_planet_radius(static_cast<float>(reference_body->radius));
|
|
else
|
|
sky_pass->set_planet_radius(0.0f);
|
|
}
|
|
}
|
|
}
|
|
|
|
void astronomy::on_observer_modified(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == observer_eid)
|
|
observer_modified();
|
|
}
|
|
|
|
void astronomy::on_observer_destroyed(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == observer_eid)
|
|
observer_modified();
|
|
}
|
|
|
|
void astronomy::on_celestial_body_modified(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == reference_body_eid)
|
|
reference_body_modified();
|
|
}
|
|
|
|
void astronomy::on_celestial_body_destroyed(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == reference_body_eid)
|
|
reference_body_modified();
|
|
}
|
|
|
|
void astronomy::on_orbit_modified(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == reference_body_eid)
|
|
reference_orbit_modified();
|
|
}
|
|
|
|
void astronomy::on_orbit_destroyed(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == reference_body_eid)
|
|
reference_orbit_modified();
|
|
}
|
|
|
|
void astronomy::on_atmosphere_modified(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == reference_body_eid)
|
|
reference_atmosphere_modified();
|
|
}
|
|
|
|
void astronomy::on_atmosphere_destroyed(entity::registry& registry, entity::id entity_id)
|
|
{
|
|
if (entity_id == reference_body_eid)
|
|
reference_atmosphere_modified();
|
|
}
|
|
|
|
void astronomy::observer_modified()
|
|
{
|
|
// Get pointer to observer component
|
|
const auto observer = registry.try_get<component::observer>(observer_eid);
|
|
|
|
if (observer)
|
|
{
|
|
if (reference_body_eid != observer->reference_body_eid)
|
|
{
|
|
// Reference body changed
|
|
reference_body_eid = observer->reference_body_eid;
|
|
reference_body_modified();
|
|
reference_orbit_modified();
|
|
reference_atmosphere_modified();
|
|
}
|
|
|
|
if (reference_body_eid != entt::null)
|
|
{
|
|
// Get pointer to reference celestial body
|
|
const auto reference_body = registry.try_get<component::celestial_body>(reference_body_eid);
|
|
|
|
// Update BCBF to EUS transformation
|
|
if (reference_body)
|
|
update_bcbf_to_eus(*observer, *reference_body);
|
|
}
|
|
|
|
// Upload observer elevation to sky pass
|
|
if (sky_pass)
|
|
sky_pass->set_observer_elevation(static_cast<float>(observer->elevation));
|
|
}
|
|
}
|
|
|
|
void astronomy::reference_body_modified()
|
|
{
|
|
// Get pointer to reference celestial body
|
|
const auto reference_body = registry.try_get<component::celestial_body>(reference_body_eid);
|
|
|
|
if (reference_body)
|
|
{
|
|
// Get pointer to observer
|
|
const auto observer = registry.try_get<component::observer>(observer_eid);
|
|
|
|
// Update BCBF to EUS transformation
|
|
if (observer)
|
|
update_bcbf_to_eus(*observer, *reference_body);
|
|
}
|
|
|
|
// Update reference celestial body-related sky pass parameters
|
|
if (sky_pass)
|
|
{
|
|
if (reference_body)
|
|
sky_pass->set_planet_radius(static_cast<float>(reference_body->radius));
|
|
else
|
|
sky_pass->set_planet_radius(0.0f);
|
|
}
|
|
}
|
|
|
|
void astronomy::reference_orbit_modified()
|
|
{
|
|
|
|
}
|
|
|
|
void astronomy::reference_atmosphere_modified()
|
|
{
|
|
|
|
}
|
|
|
|
void astronomy::update_bcbf_to_eus(const game::component::observer& observer, const game::component::celestial_body& body)
|
|
{
|
|
// Construct BCBF to EUS transformation
|
|
bcbf_to_eus = physics::orbit::frame::bcbf::to_enu
|
|
(
|
|
body.radius + observer.elevation,
|
|
observer.latitude,
|
|
observer.longitude
|
|
) * enu_to_eus;
|
|
}
|
|
|
|
void astronomy::update_icrf_to_eus(const game::component::celestial_body& body, const game::component::orbit& orbit)
|
|
{
|
|
// Evaluate reference body orientation polynomials
|
|
const double body_pole_ra = math::polynomial::horner(body.pole_ra.begin(), body.pole_ra.end(), time_centuries);
|
|
const double body_pole_dec = math::polynomial::horner(body.pole_dec.begin(), body.pole_dec.end(), time_centuries);
|
|
const double body_prime_meridian = math::polynomial::horner(body.prime_meridian.begin(), body.prime_meridian.end(), time_days);
|
|
|
|
// Construct ICRF frame to BCBF transformation
|
|
math::transformation::se3<double> icrf_to_bcbf = physics::orbit::frame::bci::to_bcbf
|
|
(
|
|
body_pole_ra,
|
|
body_pole_dec,
|
|
body_prime_meridian
|
|
);
|
|
icrf_to_bcbf.t = icrf_to_bcbf.r * -orbit.position;
|
|
|
|
/// Construct ICRF to EUS transformation
|
|
icrf_to_eus = icrf_to_bcbf * bcbf_to_eus;
|
|
|
|
// Pass ICRF to EUS transformation to sky pass
|
|
if (sky_pass)
|
|
{
|
|
// Upload topocentric frame to sky pass
|
|
sky_pass->set_icrf_to_eus
|
|
(
|
|
math::transformation::se3<float>
|
|
{
|
|
float3(icrf_to_eus.t),
|
|
math::quaternion<float>(icrf_to_eus.r)
|
|
}
|
|
);
|
|
}
|
|
}
|
|
|
|
double3 astronomy::integrate_transmittance(const game::component::observer& observer, const game::component::celestial_body& body, const game::component::atmosphere& atmosphere, geom::ray<double> ray) const
|
|
{
|
|
double3 transmittance = {1, 1, 1};
|
|
|
|
// Make ray height relative to center of reference body
|
|
ray.origin.y() += body.radius + observer.elevation;
|
|
|
|
// Construct sphere representing upper limit of the atmosphere
|
|
geom::sphere<double> atmosphere_sphere;
|
|
atmosphere_sphere.center = {0, 0, 0};
|
|
atmosphere_sphere.radius = body.radius + atmosphere.upper_limit;
|
|
|
|
// Check for intersection between the ray and atmosphere
|
|
auto intersection = geom::ray_sphere_intersection(ray, atmosphere_sphere);
|
|
if (std::get<0>(intersection))
|
|
{
|
|
// Get point of intersection
|
|
const double3 intersection_point = ray.extrapolate(std::get<2>(intersection));
|
|
|
|
// Integrate optical of Rayleigh, Mie, and ozone particles
|
|
const double optical_depth_r = physics::gas::atmosphere::optical_depth_exp(ray.origin, intersection_point, body.radius, atmosphere.rayleigh_scale_height, transmittance_samples);
|
|
const double optical_depth_m = physics::gas::atmosphere::optical_depth_exp(ray.origin, intersection_point, body.radius, atmosphere.mie_scale_height, transmittance_samples);
|
|
const double optical_depth_o = physics::gas::atmosphere::optical_depth_tri(ray.origin, intersection_point, body.radius, atmosphere.ozone_lower_limit, atmosphere.ozone_upper_limit, atmosphere.ozone_mode, transmittance_samples);
|
|
|
|
// Calculate transmittance factor due to scattering and absorption
|
|
const double3 extinction_r = atmosphere.rayleigh_scattering * optical_depth_r;
|
|
const double extinction_m = atmosphere.mie_extinction * optical_depth_m;
|
|
const double3 extinction_o = atmosphere.ozone_absorption * optical_depth_o;
|
|
transmittance = extinction_r + double3{extinction_m, extinction_m, extinction_m} + extinction_o;
|
|
transmittance.x() = std::exp(-transmittance.x());
|
|
transmittance.y() = std::exp(-transmittance.y());
|
|
transmittance.z() = std::exp(-transmittance.z());
|
|
}
|
|
|
|
return transmittance;
|
|
}
|
|
|
|
} // namespace system
|
|
} // namespace game
|