Python script for plotting the evolution of charts such as Paraview does

Question

I want to code a python script that generates a plot like the one shown to the right in the next screenshot from Paraview:

I have a series of files generated with the command foamToVTK:

Is there in VTK any function similar to PlotOverLine method of Paraview?

Answer 1

Inspired by @Nico Vuaille and https://stackoverflow.com/a/21990296/4286662 answers, I came across another different solution based on probe filters. This solution remains faithfully to the Paraview results. This is the working code:

from vtk.util import numpy_support as VN
from matplotlib import pyplot as plt
import vtk
import numpy as np
from os import walk, path, system
import pandas as pd

def getFilenames():
    ### Get the file names of each step of the simulation
    (dirpath, dirnames, filenames) = next(walk('VTK'))
    ids=[]
    for dir in dirnames:
        ids.append(int(dir.split("_")[1]))
    ids = sorted(ids)
    basename = dirnames[0].split("_")[0]

    return ids, basename, dirpath

def createLine(p1, p2):
    # Create the line along which you want to sample
    line = vtk.vtkLineSource()
    line.SetResolution(numPoints)
    line.SetPoint1(p1)
    line.SetPoint2(p2)
    line.Update()
    return line

def probeOverLine(line,reader):
    ### Interpolate the data from the VTK-file on the created line.
    probe = vtk.vtkProbeFilter()
    probe.SetInputConnection(line.GetOutputPort())
    probe.SetSourceConnection(reader.GetOutputPort())
    probe.Update()
    ### Get the velocity from the probe
    return VN.vtk_to_numpy(probe.GetOutput().GetPointData().GetArray('U'))


### Initialization of variables
cnt=1
fig= plt.figure()
numPoints=100

ids, basename, dirpath = getFilenames()

### Iteration of time steps
for id in ids[1:]:
    ### Read values from the file of this time step
    filename = "%s/%s_%d/internal.vtu" % (dirpath, basename, id)
    reader = vtk.vtkXMLUnstructuredGridReader()
    reader.SetFileName(filename)
    reader.Update()

    if cnt==1:
        ### Get points for a line in the center of the object
        bounds = reader.GetOutput().GetBounds()
        p1 = [(bounds[1] - bounds[0]) / 2.0 + bounds[0], bounds[2], 0]
        p2 = [(bounds[3] - bounds[2]) / 2.0 + bounds[2], bounds[3], 0]
        line = createLine(p1, p2)

    plotOverLine = probeOverLine(line, reader)

    df = pd.DataFrame(plotOverLine, columns=['X', 'Y', 'Z'])
    plt.clf()
    plt.title('Frame %d' % cnt)
    plt.plot(df)
    plt.legend(df.columns)
    axes = plt.gca()
    plt.draw()
    plt.pause(.05)

    cnt+=1

plt.show()

With the following result: