test_meshProperties.py

import numpy
import pytest

from stl import stl


tolerance = 1e-6


def test_mass_properties_for_half_donut(binary_ascii_path, speedups):
    """
    Checks the results of method get_mass_properties() on
    STL ASCII and binary files HalfDonut.stl
    One checks the results obtained with stl
    with the ones obtained with meshlab
    """
    filename = binary_ascii_path.join('HalfDonut.stl')
    mesh = stl.StlMesh(str(filename), speedups=speedups)
    volume, cog, inertia = mesh.get_mass_properties()
    assert(abs(volume - 2.343149) < tolerance)
    assert(numpy.allclose(cog,
           numpy.array([1.500001, 0.209472, 1.500001]),
           atol=tolerance))
    assert(numpy.allclose(inertia,
           numpy.array([[+1.390429, +0.000000, +0.000000],
                        [+0.000000, +2.701025, +0.000000],
                        [+0.000000, +0.000000, +1.390429]]),
           atol=tolerance))


def test_mass_properties_for_moon(binary_ascii_path, speedups):
    """
    Checks the results of method get_mass_properties() on
    STL ASCII and binary files Moon.stl
    One checks the results obtained with stl
    with the ones obtained with meshlab
    """
    filename = binary_ascii_path.join('Moon.stl')
    mesh = stl.StlMesh(str(filename), speedups=speedups)
    volume, cog, inertia = mesh.get_mass_properties()
    assert(abs(volume - 0.888723) < tolerance)
    assert(numpy.allclose(cog,
           numpy.array([0.906913, 0.170731, 1.500001]),
           atol=tolerance))
    assert(numpy.allclose(inertia,
           numpy.array([[+0.562097, -0.000457, +0.000000],
                        [-0.000457, +0.656851, +0.000000],
                        [+0.000000, +0.000000, +0.112465]]),
           atol=tolerance))


@pytest.mark.parametrize('filename', ('Star.stl', 'StarWithEmptyHeader.stl'))
def test_mass_properties_for_star(binary_ascii_path, filename, speedups):
    """
    Checks the results of method get_mass_properties() on
    STL ASCII and binary files Star.stl and
    STL binary file StarWithEmptyHeader.stl (with no header)
    One checks the results obtained with stl
    with the ones obtained with meshlab
    """
    filename = binary_ascii_path.join(filename)
    if not filename.exists():
        pytest.skip('STL file does not exist')
    mesh = stl.StlMesh(str(filename), speedups=speedups)
    volume, cog, inertia = mesh.get_mass_properties()
    assert(abs(volume - 1.416599) < tolerance)
    assert(numpy.allclose(cog,
           numpy.array([1.299040, 0.170197, 1.499999]),
           atol=tolerance))
    assert(numpy.allclose(inertia,
           numpy.array([[+0.509549, +0.000000, -0.000000],
                        [+0.000000, +0.991236, +0.000000],
                        [-0.000000, +0.000000, +0.509550]]),
           atol=tolerance))