Compare Field Across Mesh RegionsΒΆ

Here is some velocity data from a glacier modelling simulation that is compared across nodes in the simulation. We have simplified the mesh to have the simulation node value already on the mesh.

This was originally posted to pyvista/pyvista-support#83.

The modeling results are courtesy of Urruty Benoit and are from the Elmer/Ice simulation software.

# sphinx_gallery_thumbnail_number = 2
import pyvista as pv
from pyvista import examples
import numpy as np

# Load the sample data
mesh = examples.download_antarctica_velocity()
mesh["magnitude"] = np.linalg.norm(mesh["ssavelocity"], axis=1)
mesh
HeaderData Arrays
PolyDataInformation
N Cells1106948
N Points557470
X Bounds-2.506e+06, 2.743e+06
Y Bounds-2.143e+06, 2.240e+06
Z Bounds0.000e+00, 0.000e+00
N Arrays3
NameFieldTypeN CompMinMax
ssavelocityPointsfloat643-4.341e+039.677e+03
node_valuePointsint6410.000e+002.300e+01
magnitudePointsfloat6416.649e-031.013e+04


Here is a helper to extract regions of the mesh based on the simulation node.

def extract_node(node):
    idx = mesh["node_value"] == node
    return mesh.extract_points(idx)
p = pv.Plotter()
p.add_mesh(mesh, scalars="node_value")
for node in np.unique(mesh["node_value"]):
    loc = extract_node(node).center
    p.add_point_labels(loc, ["Node {}".format(node)])
p.show(cpos="xy")
../../_images/sphx_glr_antarctica-compare_001.png

Out:

[(118637.09504000004, 48407.14021500014, 13210946.134298638),
 (118637.09504000004, 48407.14021500014, 0.0),
 (0.0, 1.0, 0.0)]
vel_dargs = dict(scalars="magnitude", clim=[1e-3, 1e4], cmap='Blues', log_scale=True)

mesh.plot(cpos="xy", **vel_dargs)
../../_images/sphx_glr_antarctica-compare_002.png

Out:

[(118637.09504000004, 48407.14021500014, 13210946.134298638),
 (118637.09504000004, 48407.14021500014, 0.0),
 (0.0, 1.0, 0.0)]
a = extract_node(12)
b = extract_node(20)
pl = pv.Plotter()
pl.add_mesh(a, **vel_dargs)
pl.add_mesh(b, **vel_dargs)
pl.show(cpos='xy')
../../_images/sphx_glr_antarctica-compare_003.png

Out:

[(-1204058.921875, 259736.90625, 3426819.6061837124),
 (-1204058.921875, 259736.90625, 0.0),
 (0.0, 1.0, 0.0)]

plot vectors without mesh

pl = pv.Plotter()
pl.add_mesh(a.glyph(orient="ssavelocity", factor=20), **vel_dargs)
pl.add_mesh(b.glyph(orient="ssavelocity", factor=20), **vel_dargs)
pl.camera_position = [(-1114684.6969340036, 293863.65389149904, 752186.603224546),
 (-1114684.6969340036, 293863.65389149904, 0.0),
 (0.0, 1.0, 0.0)]
pl.show()
../../_images/sphx_glr_antarctica-compare_004.png

Out:

[(-1114684.6969340036, 293863.65389149904, 752186.603224546),
 (-1114684.6969340036, 293863.65389149904, 0.0),
 (0.0, 1.0, 0.0)]

Compare directions. Normalize them so we can get a reasonable direction comparison.

flow_a = a.point_arrays['ssavelocity'].copy()
flow_a /= np.linalg.norm(flow_a, axis=1).reshape(-1, 1)
flow_b = b.point_arrays['ssavelocity'].copy()
flow_b /= np.linalg.norm(flow_b, axis=1).reshape(-1, 1)


# plot normalized vectors
pl = pv.Plotter()
pl.add_arrows(a.points, flow_a, mag=10000, color='b', label='flow_a')
pl.add_arrows(b.points, flow_b, mag=10000, color='r', label='flow_b')
pl.add_legend()
pl.camera_position = [(-1044239.3240694795, 354805.0268606294, 484178.24825854995),
                      (-1044239.3240694795, 354805.0268606294, 0.0),
                      (0.0, 1.0, 0.0)]
pl.show()
../../_images/sphx_glr_antarctica-compare_005.png

Out:

[(-1044239.3240694795, 354805.0268606294, 484178.24825854995),
 (-1044239.3240694795, 354805.0268606294, 0.0),
 (0.0, 1.0, 0.0)]

flow_a that agrees with the mean flow path of flow_b

agree = flow_a.dot(flow_b.mean(0))

pl = pv.Plotter()
pl.add_mesh(a, scalars=agree, cmap='bwr', stitle='Flow agreement with block b')
pl.add_mesh(b, color='w')
pl.show(cpos='xy')
../../_images/sphx_glr_antarctica-compare_006.png

Out:

[(-1204058.921875, 259736.90625, 3426819.6061837124),
 (-1204058.921875, 259736.90625, 0.0),
 (0.0, 1.0, 0.0)]
agree = flow_b.dot(flow_a.mean(0))

pl = pv.Plotter()
pl.add_mesh(a, color='w')
pl.add_mesh(b, scalars=agree, cmap='bwr', stitle='Flow agreement with block a')
pl.show(cpos='xy')
../../_images/sphx_glr_antarctica-compare_007.png

Out:

[(-1204058.921875, 259736.90625, 3426819.6061837124),
 (-1204058.921875, 259736.90625, 0.0),
 (0.0, 1.0, 0.0)]

Total running time of the script: ( 0 minutes 20.795 seconds)

Gallery generated by Sphinx-Gallery