for(unsigned chunk_y=0; chunk_y<canvas.size.hei; chunk_y+=chunk_size) {
            for(unsigned chunk_x=0; chunk_x<canvas.size.wid; chunk_x+=chunk_size) {
                // update LRU cache and load missing tiles
                // [...]

                for(unsigned i=0; i<thread_count; ++i)
                {
                    const unsigned chunk_pos = chunk_y + chunk_min_hei * i;
                    unsigned chunk_hei =
                            (i+1 < thread_count)?
                            chunk_min_hei: chunk_size - chunk_min_hei * i;

                    threads[i] = std::thread(&Fuse::processChunk, this,
                        std::ref(canvas), std::ref(images), std::ref(tiles_indices),
                        chunk_x, chunk_pos, chunk_size, chunk_hei, std::ref(pano));
                }

                for(unsigned i=0; i<thread_count; ++i) {
                    threads[i].join();
                }

                // unload useless tiles
                // [...]
            }
        }