Contouring

Generate iso-lines or -surfaces for the scalars of a surface or volume.

3D meshes can have 2D iso-surfaces of a scalar field extracted and 2D surface meshes can have 1D iso-lines of a scalar field extracted.

from __future__ import annotations

import numpy as np

import pyvista as pv
from pyvista import examples

Iso-Lines

Let’s extract 1D iso-lines of a scalar field from a 2D surface mesh.

mesh = examples.load_random_hills()

contours = mesh.contour()

pl = pv.Plotter()
pl.add_mesh(mesh, opacity=0.85)
pl.add_mesh(contours, color="white", line_width=5)
pl.show()

Static Scene

Interactive Scene

Iso-Surfaces

Let’s extract 2D iso-surfaces of a scalar field from a 3D mesh.

mesh = examples.download_embryo()

contours = mesh.contour(np.linspace(50, 200, 5))

pl = pv.Plotter()
pl.add_mesh(mesh.outline(), color="k")
pl.add_mesh(contours, opacity=0.25, clim=[0, 200])
pl.camera_position = [
    (-130.99381142132086, 644.4868354828589, 163.80447435848686),
    (125.21748748157661, 123.94368717158413, 108.83283586619626),
    (0.2780372840777734, 0.03547871361794171, 0.9599148553609699),
]
pl.show()

Static Scene

Interactive Scene

Banded Contours

Create banded contours for surface meshes using contour_banded().

mesh = examples.load_random_hills()

Set number of contours and produce mesh and lines

n_contours = 8
contours, edges = mesh.contour_banded(n_contours)

Also make normal vectors

arrows = mesh.glyph(scale="Normals", orient="Normals", tolerance=0.05)

# Common display arguments
dargs = dict(scalars='Elevation', n_colors=n_contours - 1, cmap='Set3')

pl = pv.Plotter()
pl.add_mesh(edges, line_width=5, render_lines_as_tubes=True, color='k')
pl.add_mesh(contours, **dargs)
pl.add_mesh(arrows, **dargs)
pl.show()

Static Scene

Interactive Scene

Contours from a label map

Create labeled surfaces from 3D label maps (e.f. multi-label image segmentation) using contour_labeled(). Requires VTK version 9.3

if pv.vtk_version_info >= (9, 3):
    label_map = pv.examples.load_frog_tissues()
    mesh = label_map.contour_labeled(smoothing=True)
    mesh.plot(cmap="glasbey", cpos="yx", show_scalar_bar=False, clim=mesh.get_data_range())

Static Scene

Interactive Scene