Wrong computation of first (centroid) moment of Polyhedron

[prince2110]

For the following Polyhedron, the centroid is at (1.5, 1.5, 1.5) but instead PolyClipper gives (1.500000, 1.125000, 1.125000):

import PolyClipper as pc

dummy_vertex_list = [[0.0, 0.0, 0.0], [3.0, 0.0, 0.0], [0.0, 3.0, 0.0], [3.0, 3.0, 0.0], [0.0, 0.0, 3.0], [3.0, 0.0, 3.0], [0.0, 3.0, 3.0], [3.0, 3.0, 3.0]]
dummy_all_vertex_neighbor_list = [[1, 2, 4], [0, 3, 5], [0, 3, 6], [1, 2, 7], [0, 5, 6], [1, 4, 7], [2, 4, 7], [3, 5, 6]]

polyhedron_vertices = [pc.Vector3d(*coords) for coords in dummy_vertex_list]
poly = pc.Polyhedron()
pc.initializePolyhedron(poly, polyhedron_vertices, dummy_all_vertex_neighbor_list)
print("poly:", poly)
print("moments: ", pc.moments(poly))

The output obtained is:

('poly:', Polyhedron[Vertex3d[ ( 0 0 0) [1 2 4 ] 1 -1], Vertex3d[ ( 3 0 0) [0 3 5 ] 1 -1], Vertex3d[ ( 0 3 0) [0 3 6 ] 1 -1], Vertex3d[ ( 3 3 0) [1 2 7 ] 1 -1], Vertex3d[ ( 0 0 3) [0 5 6 ] 1 -1], Vertex3d[ ( 3 0 3) [1 4 7 ] 1 -1], Vertex3d[ ( 0 3 3) [2 4 7 ] 1 -1], Vertex3d[ ( 3 3 3) [3 5 6 ] 1 -1]])
('moments: ', (9.0, (1.500000, 1.125000, 1.125000)))

Where am I going wrong? Please help!!

[jmikeowen]

The centroid operation is not correct yet, that needs to be fixed in a future update. This is mentioned in the documentation:

https://polyclipper.readthedocs.io/en/latest/polygon_methods.html

This has been considered low-priority as we have mostly been interested the clipping operations, though it is something to be fixed.