“…Instead of uniform grids, hierarchical space partitioning structures (e.g., kd-trees, lattices) can be used to define regular convolutions [26,27,28,29,30]. Another type of networks incorporate point-wise convolution operators to directly process point clouds [31,32,33,34,35,36,37,38,39,40,41,42]. Alternatively, shapes can be treated as graphs by connecting each point to other points within neighborhoods in a feature space.…”