Thanks, Ebrahim.
Thank you for telling me the way to create the volume node.
However,if I want to save the numpy array as .vtk file,actually it’s quite simple as follows:
f = open('test.vtk','w') # change your vtk file name
f.write('# vtk DataFile Version 2.0\n')
f.write('test\n')
f.write('ASCII\n')
f.write('DATASET STRUCTURED_POINTS\n')
f.write('DIMENSIONS 3 3 4\n') # change your dimension
f.write('SPACING 0.100000 0.100000 0.100000\n')
f.write('ORIGIN 0 0 0\n')
f.write('POINT_DATA 36\n') # change the number of point data
f.write('SCALARS volume_scalars float 1\n')
f.write('LOOKUP_TABLE default\n')
f.write(numpy_array) # change your numpy array here but need some processing
f.close()