Step through a multi-step file

An FRD file stores one result block per step. pyvista_frd.FRDReader implements PyVista’s TimeReader interface.

The file here is a modal analysis: CalculiX writes one step per mode, and the “time value” of each is the natural frequency in Hz.

from pathlib import Path

import numpy as np
import pyvista as pv

import pyvista_frd

# Sphinx-Gallery runs this file from ``doc/examples``.
DATA = Path('../_data').resolve()

reader = pyvista_frd.FRDReader(DATA / 'modes.frd')

List the available modes.

print(f'{reader.number_time_points} steps')
for i, value in enumerate(reader.time_values):
    print(f'  mode {i + 1}: {value:10.2f} Hz')

4 steps
  mode 1:     755.57 Hz
  mode 2:    4406.90 Hz
  mode 3:    5008.47 Hz
  mode 4:    8669.44 Hz

Select and read one step. Opening the file indexes each result block; values are parsed when their step is first requested.

reader.set_active_time_point(0)
first = reader.read()
print(f'mode 1 peak displacement: {first.point_data["DISP"].max():.4f}')

mode 1 peak displacement: 9.7822

Plot each mode on its deformed shape.

pl = pv.Plotter(shape=(2, 2), window_size=(1100, 620))
for index in range(reader.number_time_points):
    reader.set_active_time_point(index)
    mesh = reader.read()

    # Each eigenvector has arbitrary amplitude. Scale every mode to the same
    # fraction of the beam length.
    peak = np.linalg.norm(mesh.point_data['DISP'], axis=1).max()
    warped = mesh.warp_by_vector('DISP', factor=0.12 * mesh.length / peak)

    pl.subplot(index // 2, index % 2)
    pl.add_text(f'mode {index + 1}   {reader.time_values[index]:.0f} Hz', font_size=9)
    pl.add_mesh(warped, scalars='DISP', cmap='viridis', show_scalar_bar=False)
    pl.add_mesh(mesh, style='wireframe', color='lightgrey', opacity=0.4)
    pl.view_xz()
    pl.camera.zoom(1.3)
pl.show()

Select by value instead of index. The value must match a stored step exactly.

reader.set_active_time_value(reader.time_values[-1])
print(f'active step is now {reader.active_time_value:.2f} Hz')

active step is now 8669.44 Hz