culling-stage.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 <engine/render/stages/culling-stage.hpp>
#include <engine/scene/camera.hpp>
#include <engine/scene/collection.hpp>
#include <algorithm>
#include <execution>
#include <mutex>
 
namespace render {
 
void culling_stage::execute(render::context& ctx)
{
    // Get all objects in the collection
    const auto& objects = ctx.collection->get_objects();
    
    // Get camera layer mask and view frustum
    const auto camera_layer_mask = ctx.camera->get_layer_mask();
    const auto& view_frustum = ctx.camera->get_view_frustum();
    
    // Construct mutex to guard set of visible objects
    std::mutex mutex;
    
    // For each object in the scene collection
    std::for_each
    (
        std::execution::par,
        std::begin(objects),
        std::end(objects),
        [&](scene::object_base* object)
        {
            // Ignore cameras
            if (object->get_object_type_id() == scene::camera::object_type_id)
            {
                return;
            }
            
            // Cull object if it doesn't share any common layers with the camera
            if (!(object->get_layer_mask() & camera_layer_mask))
            {
                return;
            }
            
            // Cull object if it's outside of the camera view frustum
            if (!view_frustum.intersects(object->get_bounds()))
            {
                return;
            }
            
            // Insert object into set of visible objects
            std::lock_guard<std::mutex> guard(mutex);
            ctx.objects.push_back(object);
        }
    );
}
 
} // namespace render