When 0-dimensional, i.e. scalar properties are set using `set_*_property`, they cannot be queried as a NumPy array afterwards using `*_property_array`: ```python mesh = om.TriMesh() v0 = mesh.add_vertex([1,0,0]) v1 = mesh.add_vertex([0,1,0]) v2 = mesh.add_vertex([0,0,1]) mesh.set_vertex_property('foo', v0, 1.0) mesh.set_vertex_property('foo', v1, 2.0) mesh.set_vertex_property('foo', v2, 3.0) mesh.vertex_property_array('foo') # fails: # IndexError: too many indices for an array: 1 (ndim = 0) ``` Higher-dimensional-valued properties work though: ```python mesh.set_vertex_property('bar', v0, [1.0]) mesh.set_vertex_property('bar', v1, [2.0]) mesh.set_vertex_property('bar', v2, [3.0]) mesh.vertex_property_array('bar') # works: # array([[1.], # [2.], # [3.]]) ```