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- /*
- * Copyright (C) 2021 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 "ecs/systems/atmosphere-system.hpp"
- #include "physics/atmosphere.hpp"
-
- namespace ecs {
-
- atmosphere_system::atmosphere_system(ecs::registry& registry):
- entity_system(registry)
- {
- // RGB wavelengths determined by matching wavelengths to XYZ, transforming XYZ to ACEScg, then selecting the max wavelengths for R, G, and B.
- rgb_wavelengths_nm = {602.224, 541.069, 448.143};
- rgb_wavelengths_m = rgb_wavelengths_nm * 1e-9;
-
- registry.on_construct<ecs::atmosphere_component>().connect<&atmosphere_system::on_atmosphere_construct>(this);
- registry.on_replace<ecs::atmosphere_component>().connect<&atmosphere_system::on_atmosphere_replace>(this);
- }
-
- void atmosphere_system::update(double t, double dt)
- {}
-
- void atmosphere_system::update_coefficients(ecs::entity entity)
- {
- // Abort if entity has no atmosphere component
- if (!registry.has<atmosphere_component>(entity))
- return;
-
- // Get atmosphere component of the entity
- atmosphere_component& atmosphere = registry.get<atmosphere_component>(entity);
-
- // Calculate polarization factors
- const double rayleigh_polarization = physics::atmosphere::polarization(atmosphere.index_of_refraction, atmosphere.rayleigh_density);
- const double mie_polarization = physics::atmosphere::polarization(atmosphere.index_of_refraction, atmosphere.mie_density);
-
- // Calculate Rayleigh scattering coefficients
- atmosphere.rayleigh_scattering =
- {
- physics::atmosphere::scattering_rayleigh(rgb_wavelengths_m.x, atmosphere.rayleigh_density, rayleigh_polarization),
- physics::atmosphere::scattering_rayleigh(rgb_wavelengths_m.y, atmosphere.rayleigh_density, rayleigh_polarization),
- physics::atmosphere::scattering_rayleigh(rgb_wavelengths_m.z, atmosphere.rayleigh_density, rayleigh_polarization)
- };
-
- // Calculate Mie scattering coefficients
- const double mie_scattering = physics::atmosphere::scattering_mie(atmosphere.mie_density, mie_polarization);
- atmosphere.mie_scattering =
- {
- mie_scattering,
- mie_scattering,
- mie_scattering
- };
- }
-
- void atmosphere_system::on_atmosphere_construct(ecs::registry& registry, ecs::entity entity, ecs::atmosphere_component& atmosphere)
- {
- update_coefficients(entity);
- }
-
- void atmosphere_system::on_atmosphere_replace(ecs::registry& registry, ecs::entity entity, ecs::atmosphere_component& atmosphere)
- {
- update_coefficients(entity);
- }
-
- } // namespace ecs
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