camera-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/camera-system.hpp"
#include "game/components/autofocus-component.hpp"
#include "game/components/spring-arm-component.hpp"
#include "game/components/scene-component.hpp"
#include <engine/animation/ease.hpp>
#include <engine/math/projection.hpp>
#include <engine/scene/camera.hpp>
#include <engine/math/euler-angles.hpp>
#include <execution>
 
camera_system::camera_system(entity::registry& registry):
    updatable_system(registry)
{}
 
void camera_system::update(float t, float dt)
{
    m_fixed_update_time = static_cast<double>(t);
    m_fixed_timestep = static_cast<double>(dt);
}
 
void camera_system::interpolate(float alpha)
{
    const double variable_update_time = m_fixed_update_time + m_fixed_timestep * static_cast<double>(alpha);
    const double variable_timestep = std::max(0.0, variable_update_time - m_variable_update_time);
    m_variable_update_time = variable_update_time;
    
    /*
    auto autofocus_group = registry.group<autofocus_component>(entt::get<scene_component>);
    std::for_each
    (
        std::execution::seq,
        autofocus_group.begin(),
        autofocus_group.end(),
        [&](auto entity_id)
        {
            auto& autofocus = autofocus_group.get<autofocus_component>(entity_id);
            auto& camera = static_cast<scene::camera&>(*autofocus_group.get<scene_component>(entity_id).object);
            
            // Clamp zoom factor
            autofocus.zoom = std::min<double>(std::max<double>(autofocus.zoom, 0.0), 1.0);
            
            // Calculate horizontal and vertical FoV
            autofocus.hfov = ease<double, double>::out_sine(autofocus.far_hfov, autofocus.near_hfov, autofocus.zoom);
            autofocus.vfov = math::vertical_fov(autofocus.hfov, static_cast<double>(camera.get_aspect_ratio()));
            
            // Calculate focal plane dimensions
            autofocus.focal_plane_size.y() = ease<double, double>::out_sine(autofocus.far_focal_plane_height, autofocus.near_focal_plane_height, autofocus.zoom);
            autofocus.focal_plane_size.x() = autofocus.focal_plane_size.y() * static_cast<double>(camera.get_aspect_ratio());
            
            // Calculate focal distance
            autofocus.focal_distance = autofocus.focal_plane_height * 0.5 / std::tan(autofocus.vfov * 0.5);
            
            // Update camera projection matrix
            camera.set_vertical_fov(static_cast<float>(autofocus.vfov));
        }
    );
    */
    
    auto spring_arm_group = registry.group<spring_arm_component>(entt::get<scene_component>);
    std::for_each
    (
        std::execution::seq,
        spring_arm_group.begin(),
        spring_arm_group.end(),
        [&](auto entity_id)
        {
            auto& spring_arm = spring_arm_group.get<spring_arm_component>(entity_id);
            auto& camera = static_cast<scene::camera&>(*spring_arm_group.get<scene_component>(entity_id).object);
            
            math::transform<double> parent_transform = math::transform<double>::identity();
            if (spring_arm.parent_eid != entt::null)
            {
                const auto parent_scene = registry.try_get<scene_component>(spring_arm.parent_eid);
                if (parent_scene)
                {
                    parent_transform.translation = math::dvec3(parent_scene->object->get_translation());
                    parent_transform.rotation = math::dquat(parent_scene->object->get_rotation());
                }
            }
            
            // Calculate focal point
            spring_arm.focal_point_spring.set_target_value(parent_transform * spring_arm.focal_point_offset);
            
            // Integrate angular velocities
            spring_arm.angles_spring.set_target_value(spring_arm.angles_spring.get_target_value() + spring_arm.angular_velocities * variable_timestep);
            
            // Apply angular constraints
            spring_arm.angles_spring.set_target_value(math::clamp(spring_arm.angles_spring.get_target_value(), spring_arm.min_angles, spring_arm.max_angles));
            
            // Solve springs
            spring_arm.focal_point_spring.solve(variable_timestep);
            spring_arm.angles_spring.solve(variable_timestep);
            
            // Recalculate zoom
            // if (spring_arm.pitch_velocity)
            {
                spring_arm.zoom = ease<double, double>::in_sine(1.0, 0.0, spring_arm.angles_spring.get_value().x() / -math::half_pi<double>);
            }
            
            // Clamp zoom
            spring_arm.zoom = std::min<double>(std::max<double>(spring_arm.zoom, 0.0), 1.0);
            
            // Update FoV
            spring_arm.hfov = ease<double, double>::out_sine(spring_arm.far_hfov, spring_arm.near_hfov, spring_arm.zoom);
            spring_arm.vfov = math::vertical_fov(spring_arm.hfov, static_cast<double>(camera.get_aspect_ratio()));
            
            // Update focal plane size
            spring_arm.focal_plane_height = ease<double, double>::out_sine(spring_arm.far_focal_plane_height, spring_arm.near_focal_plane_height, spring_arm.zoom);
            spring_arm.focal_plane_width = spring_arm.focal_plane_height * static_cast<double>(camera.get_aspect_ratio());
            
            // Update focal distance
            spring_arm.focal_distance = spring_arm.focal_plane_height * 0.5 / std::tan(spring_arm.vfov * 0.5);
            
            const auto camera_up = spring_arm.up_rotation * math::dvec3{0, 1, 0};
            const auto parent_up = parent_transform.rotation * math::dvec3{0, 1, 0};
            spring_arm.up_rotation = math::normalize(math::rotation(camera_up, parent_up) * spring_arm.up_rotation);
            
            // Update camera rotation
            spring_arm.camera_rotation = math::normalize(spring_arm.up_rotation * math::euler_xyz_to_quat(spring_arm.angles_spring.get_value()));
            
            // Update transform
            const auto camera_translation = spring_arm.focal_point_spring.get_value() + spring_arm.camera_rotation * math::dvec3{0.0f, 0.0f, spring_arm.focal_distance};
            
            math::transform<float> camera_transform;
            camera_transform.translation = math::fvec3(camera_translation);
            camera_transform.rotation = math::fquat(spring_arm.camera_rotation);
            camera_transform.scale = {1, 1, 1};
            
            
            double center_offset = (1.0 - std::abs(spring_arm.angles_spring.get_value().x()) / math::half_pi<double>) * (spring_arm.focal_plane_height / 3.0 * 0.5);
            camera_transform.translation += math::fvec3(spring_arm.camera_rotation * math::dvec3{0, center_offset, 0});
            
            camera.set_transform(camera_transform);
            camera.set_vertical_fov(static_cast<float>(spring_arm.vfov));
        }
    );
}
 
void camera_system::set_viewport(const math::fvec4& viewport)
{
    m_viewport = math::dvec4(viewport);
    m_aspect_ratio = m_viewport[2] /  m_viewport[3];
}