Add Cell Connectivity To Points

Example for PVGeo.filters.AddCellConnToPoints

This filter will add linear cell connectivity between scattered points. You have the option to add VTK_LINE or VTK_POLYLINE connectivity. VTK_LINE connectivity makes a straight line between the points in order (either in the order by index or using a nearest neighbor calculation). The VTK_POLYLINE adds polyline connectivity between all points as one spline (either in the order by index or using a nearest neighbor calculation).

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import numpy as np
import pyvista

from PVGeo import points_to_poly_data
from PVGeo.filters import AddCellConnToPoints

First, lets generate some points which we’d like to connect

def path1(y):
    """Equation: x = a(y-h)^2 + k"""
    a = -110.0 / 160.0**2
    x = a * y**2 + 110.0
    idxs = np.argwhere(x > 0)
    return x[idxs][:, 0], y[idxs][:, 0]


x, y = path1(np.arange(0.0, 200.0, 25.0))
zo = np.linspace(9.0, 11.0, num=len(y))
coords = np.vstack((x, y, zo)).T
# Shuffle points to demonstrate value of Nearest Neighbor
np.random.shuffle(coords)

# Make a VTK data object for the filter to use
vtkPoints = points_to_poly_data(coords)

Apply the Filter

Now that you have the points generated, lets go ahead and apply the Add Cell Connectivity To Points filter from Filters->PVGeo: General Filters->Add Cell Connectivity To Points. The output data should look really wacky and incorrectly built like the image below; this is good.

line = AddCellConnToPoints().apply(vtkPoints)

p = pyvista.Plotter()
p.add_mesh(line, line_width=5, point_size=10)
p.show()

Static Scene

Interactive Scene

Remember that in the script given above we shuffle the points to demonstrate that the points make a usable line but we need to reconstruct the order of the points. We do this by using the Use Nearest Nbr Approx checkbox; this will ensure that a usable path is generate from the points. Go ahead and use the nearest_nbr argument for the algorithm. Now it looks good (see image below)!

# Use the filter: Here is vtkPolyData containing the connected line:
line_o = AddCellConnToPoints(nearest_nbr=True).apply(vtkPoints)

p = pyvista.Plotter()
p.add_mesh(line_o, line_width=5, point_size=10)
p.show()

Static Scene

Interactive Scene