source/src/game/systems/steering-system.cpp

/*
 * 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;
				}
			);
		}
	);
}