Clipping with a Surface

Clip any PyVista dataset by a pyvista.PolyData surface mesh using the pyvista.DataSetFilters.clip_surface() filter.

Note that we first demonstrate how the clipping is performed by computing an implicit distance and thresholding the mesh. This thresholding is one approach to clip by a surface, and preserve the original geometry of the given mesh, but many folks leverage the clip_surface filter to triangulate/tessellate the mesh geometries along the clip.

import numpy as np

import pyvista as pv
from pyvista import examples

surface = pv.Cone(direction=(0, 0, -1), height=3.0, radius=1, resolution=50, capping=False)

# Make a gridded dataset
n = 51
xx = yy = zz = 1 - np.linspace(0, n, n) * 2 / (n - 1)
dataset = pv.RectilinearGrid(xx, yy, zz)

# Preview the problem
p = pv.Plotter()
p.add_mesh(surface, color='w', label='Surface')
p.add_mesh(dataset, color='gold', show_edges=True, opacity=0.75, label='To Clip')
p.add_legend()
p.show()

Take a look at the implicit function used to perform the surface clipping by using the pyvista.DataSetFilters.compute_implicit_distance() filter. The clipping operation field is performed where the implicit_distance field is zero and the invert flag controls which sides of zero to preserve.

dataset.compute_implicit_distance(surface, inplace=True)

inner = dataset.threshold(0.0, scalars="implicit_distance", invert=True)
outer = dataset.threshold(0.0, scalars="implicit_distance", invert=False)

p = pv.Plotter()
p.add_mesh(surface, color='w', label='Surface', opacity=0.75)
p.add_mesh(
    inner,
    scalars="implicit_distance",
    show_edges=True,
    opacity=0.75,
    label='Inner region',
    clim=[-1, 1],
    cmap="bwr",
)
p.add_legend()
p.show()

p = pv.Plotter()
p.add_mesh(surface, color='w', label='Surface', opacity=0.75)
p.add_mesh(
    outer,
    scalars="implicit_distance",
    show_edges=True,
    opacity=0.75,
    label='Outer region',
    clim=[-1, 1],
    cmap="bwr",
)
p.add_legend()
p.show()

Clip the rectilinear grid dataset using the pyvista.PolyData surface mesh via the pyvista.DataSetFilters.clip_surface() filter. This will triangulate/tessellate the mesh geometries along the clip.

clipped = dataset.clip_surface(surface, invert=False)

# Visualize the results
p = pv.Plotter()
p.add_mesh(surface, color='w', opacity=0.75, label='Surface')
p.add_mesh(clipped, color='gold', show_edges=True, label="clipped", opacity=0.75)
p.add_legend()
p.show()

Here is another example of clipping a mesh by a surface. This time, we’ll generate a pyvista.UniformGrid around a topography surface and then clip that grid using the surface to create a closed 3D model of the surface

surface = examples.load_random_hills()

# Create a grid around that surface
grid = pv.create_grid(surface)

# Clip the grid using the surface
model = grid.clip_surface(surface)

# Compute height and display it
model.elevation().plot()