animation-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/animation-system.hpp"
#include "game/components/pose-component.hpp"
#include "game/components/scene-component.hpp"
#include <engine/animation/bone.hpp>
#include <engine/scene/skeletal-mesh.hpp>
#include <engine/math/interpolation.hpp>
#include <algorithm>
#include <execution>
 
animation_system::animation_system(entity::registry& registry):
    updatable_system(registry)
{}
 
void animation_system::update(float t, float dt)
{
    
}
 
void animation_system::interpolate(float alpha)
{
    auto pose_group = registry.group<pose_component>(entt::get<scene_component>);
    std::for_each
    (
        std::execution::par_unseq,
        pose_group.begin(),
        pose_group.end(),
        [&](auto entity_id)
        {
            auto& pose = pose_group.get<pose_component>(entity_id);
            auto& scene = pose_group.get<scene_component>(entity_id);
            
            auto& skeletal_mesh = static_cast<scene::skeletal_mesh&>(*scene.object);
            for (std::size_t i = 0; i < skeletal_mesh.get_skeleton()->get_bone_count(); ++i)
            {
                const auto bone_index = static_cast<bone_index_type>(i);
                const auto& previous_transform = pose.previous_pose.get_relative_transform(bone_index);
                const auto& current_transform = pose.current_pose.get_relative_transform(bone_index);
                
                // Interpolate bone pose between previous and current states
                bone_transform_type interpolated_transform;
                interpolated_transform.translation = math::lerp(previous_transform.translation, current_transform.translation, alpha);
                interpolated_transform.rotation = math::nlerp(previous_transform.rotation, current_transform.rotation, alpha);
                interpolated_transform.scale = math::lerp(previous_transform.scale, current_transform.scale, alpha);
                
                // Update skeletal mesh bone pose with interpolated transform
                skeletal_mesh.get_pose().set_relative_transform(static_cast<bone_index_type>(i), interpolated_transform);
            }
            
            // Concatenate interpolated pose
            skeletal_mesh.get_pose().update();
        }
    );
}