No Scalar quality after filter 'compute_scalar_by_distance_from_another_mesh_per_vertex'

[wsAndy]

I want to compare two meshes by pymeshlab. Here is the main code.

import pymeshlab 

ms = pymeshlab.MeshSet()
ms.load_new_mesh('./1.obj')
ms.set_current_mesh(0)

# copy  mesh
ms.generate_copy_of_current_mesh()
ms.set_current_mesh(1)

# reduce face 
ms.meshing_decimation_quadric_edge_collapse(targetperc=0.8, qualitythr = 0.9)

# calculate scalar 
ms.compute_scalar_by_distance_from_another_mesh_per_vertex(measuremesh = 1, refmesh = 0)

curMesh = ms.current_mesh() 
# print scalar
print( curMesh.vertex_scalar_array() )

But the code always print get zero-matrix .