orbit-system.cpp

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/*
 * Copyright (C) 2023  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/orbit-system.hpp"
#include <engine/physics/orbit/orbit.hpp>
 
 
orbit_system::orbit_system(entity::registry& registry):
    updatable_system(registry),
    ephemeris(nullptr),
    time(0.0),
    time_scale(1.0)
{
    registry.on_construct<::orbit_component>().connect<&orbit_system::on_orbit_construct>(this);
    registry.on_update<::orbit_component>().connect<&orbit_system::on_orbit_update>(this);
}
 
orbit_system::~orbit_system()
{
    registry.on_construct<::orbit_component>().disconnect<&orbit_system::on_orbit_construct>(this);
    registry.on_update<::orbit_component>().disconnect<&orbit_system::on_orbit_update>(this);
}
 
void orbit_system::update(float t, float dt)
{
    // Add scaled timestep to current time
    set_time(time + dt * time_scale);
    
    if (!ephemeris)
        return;
    
    // Calculate positions of ephemeris items, in meters
    for (int i: ephemeris_indices)
        positions[i] = ephemeris->trajectories[i].position(time) * 1000.0;
    
    // Propagate orbits
    registry.view<orbit_component>().each
    (
        [&](entity::id entity_eid, auto& orbit)
        {
            orbit.position = positions[orbit.ephemeris_index] * orbit.scale;
            
            entity::id parent_id = orbit.parent;
            while (parent_id != entt::null)
            {
                const orbit_component& parent_orbit = registry.get<orbit_component>(parent_id);
                orbit.position += positions[parent_orbit.ephemeris_index] * parent_orbit.scale;
                parent_id = parent_orbit.parent;
            }
        }
    );
}
 
void orbit_system::set_ephemeris(std::shared_ptr<physics::orbit::ephemeris<double>> ephemeris)
{
    this->ephemeris = ephemeris;
    positions.resize((ephemeris) ? ephemeris->trajectories.size() : 0);
}
 
void orbit_system::set_time(double time)
{
    this->time = time;
}
 
void orbit_system::set_time_scale(double scale)
{
    time_scale = scale;
}
 
void orbit_system::on_orbit_construct(entity::registry& registry, entity::id entity_id)
{
    const ::orbit_component& component = registry.get<::orbit_component>(entity_id);
    ephemeris_indices.insert(component.ephemeris_index);
}
 
void orbit_system::on_orbit_update(entity::registry& registry, entity::id entity_id)
{
    const ::orbit_component& component = registry.get<::orbit_component>(entity_id);
    ephemeris_indices.insert(component.ephemeris_index);
}