About this 3D model

This thing design features some Sierpinski pyramides that could be printed without any support structure. In each depth of the pyramide, there are 5 sub-pyramides while the central-upper one is supported by (a non-fractal) upside-down pyramide with the same size. Hence, it can easily be printed and the result will look very nice (see image), and real-world light-shade effects practically "hide" these supporting pyramides. You may able to generate any version for this using the C code attached. See __Instructions__ for further details.