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sample_arcs()

Sample mesh data along multiple circular arcs.

Creates circular arc probes for each (pointa, pointb, center) tuple and samples the mesh data onto each arc. For temporal datasets, automatically sweeps all time points unless time_value is specified.

Parameters
  • arcs (Sequence[tuple[Sequence[float], Sequence[float], Sequence[float]]]) — List of arc definitions, each as a tuple (pointa, pointb, center) where each component is an [x, y, z] coordinate.
  • resolution (int | list[int], default: 100) — Number of segments to divide each arc into. Can be a single int (applied to all arcs) or a list of ints (one per arc).
  • negative (bool, default: False) — If False, arcs span the positive angle. If True, span the negative (reflex) angle. Applied to all arcs.
  • time_value (float | None, default: None) — Query a specific time value instead of sweeping all time points. Ignored for static datasets.
  • tolerance (float | None, default: None) — Tolerance for the sample operation. If None, PyVista generates a tolerance automatically.
  • progress_callback (callable | None, default: None) — Callback function for progress updates. Called with (current_arc, total_arcs). Should return True to continue or False to cancel.
Returns

Returns a list of results (one per arc), where each result is a list of dictionaries (one per time step) with a "time" key and array names as keys. Each array has:

  • For scalars: "distance", "value", "x", "y", "z" (sample point coordinates)
  • For vectors: "distance", "x_value", "y_value", "z_value", "tangential", "normal", "x", "y", "z" (sample point coordinates)
[
    # First arc results
    [
        # Time 0
        {"time": 0.0, "scalar_name": {"distance": [...], "value": [...], "x": [...], "y": [...], "z": [...]}, ...},
        # Time 1
        {"time": 0.01, "scalar_name": {"distance": [...], "value": [...], "x": [...], "y": [...], "z": [...]}, ...},
        ...
    ],
    # Second arc results
    [
        {"time": 0.0, "scalar_name": {"distance": [...], "value": [...], "x": [...], "y": [...], "z": [...]}, ...},
        ...
    ],
    ...
]

Examples​

Sweep all time steps​

from pyemsi import Plotter, examples
from matplotlib import pyplot
import numpy as np

file_path = examples.ipm_motor_path()
plt = Plotter(file_path)

data = plt.sample_arcs(
    arcs=[
        ((0.080575, 0, 0), (0.0569751, 0.0569751, 0), (0, 0, 0)),
        ((0.0792007, 0.0167379, 0), (0.0769587, 0.0251049, 0), (0, 0, 0)),
    ],
    resolution=100,
)

fig, axes = pyplot.subplots(1, len(data), figsize=(14, 6), subplot_kw={"projection": "3d"})
axes = np.atleast_1d(axes)

for idx, arc_data in enumerate(data):
    time_values = [time_data["time"] for time_data in arc_data]
    distances = arc_data[0]["B-Mag (T)"]["distance"]
    value_grid = np.array([time_data["B-Mag (T)"]["value"] for time_data in arc_data])
    time_grid, distance_grid = np.meshgrid(time_values, distances, indexing="ij")

    axes[idx].plot_surface(time_grid, distance_grid, value_grid, cmap="viridis")
    axes[idx].set_xlabel("Time (s)")
    axes[idx].set_ylabel("Distance Along Arc (m)")
    axes[idx].set_zlabel("B-Mag (T)")
    axes[idx].set_title(f"Arc {idx + 1}")

fig.suptitle("B-Mag (T) Along Sampled Arcs")
fig.tight_layout()
fig.savefig("docs/static/demos/sample_arcs.png")

Sample Arcs

Plot three time slices​

from pyemsi import Plotter, examples
from matplotlib import pyplot
import numpy as np

file_path = examples.ipm_motor_path()
plt = Plotter(file_path)

data = plt.sample_arcs(
    arcs=[
        ((0.080575, 0, 0), (0.0569751, 0.0569751, 0), (0, 0, 0)),
        ((0.0792007, 0.0167379, 0), (0.0769587, 0.0251049, 0), (0, 0, 0)),
    ],
    resolution=100,
)

fig, axes = pyplot.subplots(1, len(data), figsize=(14, 5))
axes = np.atleast_1d(axes)

for idx, arc_data in enumerate(data):
    time_indices = sorted({0, len(arc_data) // 2, len(arc_data) - 1})

    for time_idx in time_indices:
        axes[idx].plot(
            arc_data[time_idx]["B-Mag (T)"]["distance"],
            arc_data[time_idx]["B-Mag (T)"]["value"],
            label=f"t = {arc_data[time_idx]['time']:.3f} s",
        )

    axes[idx].set_xlabel("Distance Along Arc (m)")
    axes[idx].set_ylabel("B-Mag (T)")
    axes[idx].set_title(f"Arc {idx + 1}")
    axes[idx].legend()

fig.suptitle("B-Mag (T) Along Sampled Arcs at Three Time Points")
fig.tight_layout()
fig.savefig("docs/static/demos/sample_arcs_time_slices.png")

Sample Arcs Time Slices

Plot tangential and normal B-Vec components​

from pyemsi import Plotter, examples
from matplotlib import pyplot
import numpy as np

file_path = examples.ipm_motor_path()
plt = Plotter(file_path)

data = plt.sample_arcs(
    arcs=[
        ((0.080575, 0, 0), (0.0569751, 0.0569751, 0), (0, 0, 0)),
        ((0.0792007, 0.0167379, 0), (0.0769587, 0.0251049, 0), (0, 0, 0)),
    ],
    resolution=100,
)

fig, axes = pyplot.subplots(len(data), 2, figsize=(12, 4 * len(data)))
axes = np.array(axes, dtype=object)
if axes.ndim == 1:
    axes = axes[np.newaxis, :]

for idx, arc_data in enumerate(data):
    time_indices = sorted({0, len(arc_data) // 2, len(arc_data) - 1})

    for time_idx in time_indices:
        label = f"t = {arc_data[time_idx]['time']:.3f} s"
        axes[idx, 0].plot(
            arc_data[time_idx]["B-Vec (T)"]["distance"],
            arc_data[time_idx]["B-Vec (T)"]["tangential"],
            label=label,
        )
        axes[idx, 1].plot(
            arc_data[time_idx]["B-Vec (T)"]["distance"],
            arc_data[time_idx]["B-Vec (T)"]["normal"],
            label=label,
        )

    axes[idx, 0].set_xlabel("Distance Along Arc (m)")
    axes[idx, 0].set_ylabel("Tangential B-Vec (T)")
    axes[idx, 0].set_title(f"Arc {idx + 1} Tangential")
    axes[idx, 0].legend()

    axes[idx, 1].set_xlabel("Distance Along Arc (m)")
    axes[idx, 1].set_ylabel("Normal B-Vec (T)")
    axes[idx, 1].set_title(f"Arc {idx + 1} Normal")
    axes[idx, 1].legend()

fig.suptitle("B-Vec (T) Components Along Sampled Arcs at Three Time Points")
fig.tight_layout()
fig.savefig("docs/static/demos/sample_arcs_bvec_components_time_slices.png")

Sample Arcs B-Vec Components Time Slices

See Also​