# Examples from pyvista.examples.downloads.download_coil_magnetic_field
# =====================================================================

# Download the magnetic field dataset and generate streamlines from the field.
import pyvista as pv
from pyvista import examples
grid = examples.download_coil_magnetic_field()
seed = pv.Disc(inner=1, outer=5.2, r_res=3, c_res=12)
strl = grid.streamlines_from_source(
    seed,
    vectors='B',
    max_length=180,
    initial_step_length=0.1,
    integration_direction='both',
)
strl.plot(
    cmap='plasma',
    render_lines_as_tubes=True,
    line_width=2,
    lighting=False,
    zoom=2,
)

# Plot the magnet field strength in the Z direction.
import numpy as np
import pyvista as pv
from pyvista import examples
grid = examples.download_coil_magnetic_field()
# create coils
coils = []
for z in np.linspace(-8, 8, 16):
    coils.append(
        pv.Polygon(center=(0, 0, z), radius=5, n_sides=100, fill=False)
    )
coils = pv.MultiBlock(coils)
# plot the magnet field strength in the Z direction
scalars = np.abs(grid['B'][:, 2])
pl = pv.Plotter()
_ = pl.add_mesh(coils, render_lines_as_tubes=True, line_width=5, color='w')
vol = pl.add_volume(
    grid,
    scalars=scalars,
    cmap='plasma',
    show_scalar_bar=False,
    log_scale=True,
    opacity='sigmoid_2',
)
vol.prop.interpolation_type = 'linear'
_ = pl.add_volume_clip_plane(
    vol,
    normal='-x',
    normal_rotation=False,
    interaction_event='always',
    widget_color=pv.Color(opacity=0.0),
)
pl.enable_anti_aliasing()
pl.camera.zoom(2)
pl.show()

# SEE ALSO:
#     Coil Magnetic Field Dataset https://docs.pyvista.org/api/examples/dataset_gallery.html#coil-magnetic-field-dataset
#     See this dataset in the Dataset Gallery for more info.
#     Plot a Magnetic Field https://docs.pyvista.org/examples/99-advanced/magnetic_fields.html#magnetic-fields-example
#     More details on how to plot with this dataset.

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# Generated by sphinx-examples-as-code https://github.com/pyvista/sphinx-examples-as-code