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Fix law-of-cosines typo in triangleAngleQuality #763

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Fix law-of-cosines typo in triangleAngleQuality #763

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36 changes: 36 additions & 0 deletions conda_package/tests/test_conversion.py
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,41 @@ def test_conversion_angle_edge():
assert np.max(np.abs(angle_diff)) < 1.0e-10


def test_conversion_triangle_angle_quality():
ds_mesh = xarray.open_dataset(
get_test_data_file('mesh.QU.1920km.151026.nc')
)
ds_mesh = convert(dsIn=ds_mesh)

edges_on_vertex = ds_mesh.edgesOnVertex.values - 1
assert np.all(edges_on_vertex >= 0)
dc_edge = ds_mesh.dcEdge.values
a_len = dc_edge[edges_on_vertex[:, 0]]
b_len = dc_edge[edges_on_vertex[:, 1]]
c_len = dc_edge[edges_on_vertex[:, 2]]

# law of cosines for the angle opposite each side of the dual triangle
angle1 = np.arccos(
np.clip((b_len**2 + c_len**2 - a_len**2) / (2 * b_len * c_len), -1, 1)
)
angle2 = np.arccos(
np.clip((a_len**2 + c_len**2 - b_len**2) / (2 * a_len * c_len), -1, 1)
)
angle3 = np.arccos(
np.clip((a_len**2 + b_len**2 - c_len**2) / (2 * a_len * b_len), -1, 1)
)
angles = np.stack([angle1, angle2, angle3], axis=1)
assert np.max(np.abs(angles.sum(axis=1) - np.pi)) < 1.0e-10

min_angle = angles.min(axis=1)
max_angle = angles.max(axis=1)
quality = ds_mesh.triangleAngleQuality.values
assert np.max(np.abs(quality - min_angle / max_angle)) < 1.0e-10

obtuse = (max_angle > 0.5 * np.pi).astype(int)
assert np.array_equal(ds_mesh.obtuseTriangle.values, obtuse)


def test_masks_to_int_dataset_copy():
ds_in = xarray.Dataset(
data_vars={
Expand All @@ -71,3 +106,4 @@ def test_masks_to_int_dataset_copy():
if __name__ == '__main__':
test_conversion()
test_conversion_angle_edge()
test_conversion_triangle_angle_quality()
2 changes: 1 addition & 1 deletion mesh_tools/mesh_conversion_tools/mpas_mesh_converter.cpp
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Expand Up @@ -2314,7 +2314,7 @@ int buildMeshQualities(){/*{{{*/
#endif

angle1 = acos( max(-1.0, min(1.0, (b_len * b_len + c_len * c_len - a_len * a_len) / (2 * b_len * c_len))));
angle2 = acos( max(-1.0, min(1.0, (a_len * a_len + c_len * c_len - b_len * c_len) / (2 * a_len * c_len))));
angle2 = acos( max(-1.0, min(1.0, (a_len * a_len + c_len * c_len - b_len * b_len) / (2 * a_len * c_len))));
angle3 = acos( max(-1.0, min(1.0, (a_len * a_len + b_len * b_len - c_len * c_len) / (2 * a_len * b_len))));

minAngle = min(angle1, min(angle2, angle3));
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2 changes: 1 addition & 1 deletion mesh_tools/mesh_conversion_tools_netcdf_c/mpas_mesh_converter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2395,7 +2395,7 @@ int buildMeshQualities(){/*{{{*/
angle1 = acos( max(-1.0, min(1.0,
(b_len * b_len + c_len * c_len - a_len * a_len) / (2 * b_len * c_len))));
angle2 = acos( max(-1.0, min(1.0,
(a_len * a_len + c_len * c_len - b_len * c_len) / (2 * a_len * c_len))));
(a_len * a_len + c_len * c_len - b_len * b_len) / (2 * a_len * c_len))));
angle3 = acos( max(-1.0, min(1.0,
(a_len * a_len + b_len * b_len - c_len * c_len) / (2 * a_len * b_len))));

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