steering-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/steering-system.hpp"
#include "game/components/steering-component.hpp"
#include "game/components/transform-component.hpp"
#include "game/components/winged-locomotion-component.hpp"
#include "game/components/rigid-body-component.hpp"
#include <engine/entity/id.hpp>
#include <engine/ai/steering/behavior/wander.hpp>
#include <engine/ai/steering/behavior/seek.hpp>
#include <engine/math/quaternion.hpp>
#include <engine/config.hpp>
 
steering_system::steering_system(entity::registry& registry):
    updatable_system(registry)
{}
 
void steering_system::update(float t, float dt)
{
    registry.group<steering_component>(entt::get<transform_component, winged_locomotion_component, rigid_body_component>).each
    (
        [&](entity::id entity_id, auto& steering, auto& transform, auto& locomotion, const auto& body_component)
        {
            auto& agent = steering.agent;
            auto& body = *body_component.body;
            
            // Update agent parameters
            agent.position = transform.local.translation;
            agent.orientation = transform.local.rotation;
            agent.velocity = body.get_linear_velocity();
            
            // Accumulate steering forces
            math::fvec3 force = {0, 0, 0};
            if (steering.wander_weight)
            {
                //force += ai::steering::behavior::wander_2d(agent, steering.wander_noise * dt, steering.wander_distance, steering.wander_radius, steering.wander_angle) * steering.wander_weight;
                force += ai::steering::behavior::wander_3d(agent, steering.wander_noise * dt, steering.wander_distance, steering.wander_radius, steering.wander_angle, steering.wander_angle2) * steering.wander_weight;
            }
            if (steering.seek_weight)
            {
                force += ai::steering::behavior::seek(agent, steering.seek_target) * steering.seek_weight;
            }
            
            // Normalize force
            if (steering.sum_weights)
            {
                force /= steering.sum_weights;
            }
            
            // Pass force to winged locomotion component
            registry.patch<::winged_locomotion_component>
            (
                entity_id,
                [&](auto& component)
                {
                    component.force = force;
                }
            );
            
            // Rotate agent
            const float speed_squared = math::sqr_length(agent.velocity);
            if (speed_squared)
            {
                agent.orientation = math::look_rotation(agent.velocity / std::sqrt(speed_squared), agent.up);
                agent.forward = agent.orientation * config::global_forward;
                agent.up = agent.orientation * config::global_up;
            }
            
            // Update orientation
            registry.patch<::transform_component>
            (
                entity_id,
                [&agent](auto& component)
                {
                    component.local.rotation = agent.orientation;
                }
            );
        }
    );
}