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"""
.. _magnetic_fields_example:
Plot a Magnetic Field
---------------------
The following example demonstrates how PyVista can be used to plot a magnetic
field.
This example relies on :func:`streamlines_from_source()
<pyvista.PolyDataFilters.streamlines_from_source>` to generate streamlines and
:func:`add_volume() <pyvista.Plotter.add_volume>` to plot the strength of the
magnetic field.
This dataset was created from the `Coil Field Lines
<https://magpylib.readthedocs.io/en/latest/examples/examples_30_coil_field_lines.html>`_
example from the awesome `magpylib <https://github.com/magpylib/magpylib>`_
library.
"""
# sphinx_gallery_thumbnail_number = 3
from __future__ import annotations
import numpy as np
import pyvista as pv
from pyvista import examples
# %%
# Download the DataSet
# ~~~~~~~~~~~~~~~~~~~~
# Let's first download the example dataset and show that it's a
# :class:`pyvista.ImageData` with the magnetic field stored as the ``'B'``
# array in ``point_data``.
grid = examples.download_coil_magnetic_field()
grid.point_data
# %%
# Create Coils
# ~~~~~~~~~~~~
# Create several hoops to represent the coil. This matches the geometry in the
# original example.
coils = [pv.Polygon((0, 0, z), radius=5, n_sides=100, fill=False) for z in np.linspace(-8, 8, 16)]
coil_block = pv.MultiBlock(coils)
coil_block.plot(render_lines_as_tubes=True, line_width=10)
# %%
# Compute and Plot Field Lines
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Next, let's compute streamlines from the center of the coil to represent the
# direction of the magnetic force. For this, we can create a simple
# :func:`pyvista.Disc` and use that as the source of the streamlines.
seed = pv.Disc(inner=1, outer=5.4, r_res=2, c_res=12)
strl = grid.streamlines_from_source(
seed,
vectors='B',
max_time=180,
initial_step_length=0.1,
integration_direction='both',
)
pl = pv.Plotter()
pl.add_mesh(
strl.tube(radius=0.1),
cmap='bwr',
ambient=0.2,
)
pl.add_mesh(coil_block, render_lines_as_tubes=True, line_width=5, color='w')
pl.camera.zoom(3)
pl.show()
# %%
# Plot the Magnet Field Strength
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# Finally, let's bring this all together by plotting the magnetic field
# strength while also plotting the streamlines and the coil.
# Take the norm of the magnetic field
scalars = np.linalg.norm(grid['B'], axis=1)
# Customize the opacity to make it easier to visualize the strength of the
# field nearby the coil
opacity = 1 - np.geomspace(1.0, 0.05, 10)
# sphinx_gallery_start_ignore
# volume rendering does not work in interactive plots currently
PYVISTA_GALLERY_FORCE_STATIC = True
# sphinx_gallery_end_ignore
# Add this all to the plotter
pl = pv.Plotter()
pl.add_mesh(
strl.tube(radius=0.1),
color='black',
)
pl.add_mesh(coil_block, render_lines_as_tubes=True, line_width=5, color='w')
vol = pl.add_volume(
grid,
scalars=scalars,
opacity=opacity,
cmap='hot',
show_scalar_bar=False,
)
vol.prop.interpolation_type = 'linear'
pl.camera.zoom(5)
pl.show()
|
