Extract Cells Inside Surface

Extract the cells in a mesh that exist inside or outside a closed surface of another mesh

# sphinx_gallery_thumbnail_number = 2
import pyvista as pv
from pyvista import examples

mesh = examples.download_cow()

cpos = [(13.0, 7.6, -13.85), (0.44, -0.4, -0.37), (-0.28, 0.9, 0.3)]

dargs = dict(show_edges=True)
# Rotate the mesh to have a second mesh
rot = mesh.copy()
rot.rotate_y(90)

p = pv.Plotter()
p.add_mesh(mesh, color="Crimson", **dargs)
p.add_mesh(rot, color="mintcream", opacity=0.35, **dargs)
p.camera_position = cpos
p.show()

Out:

[(13.0, 7.6, -13.85),
 (0.44, -0.4, -0.37),
 (-0.2830738875949229, 0.9098803529836806, 0.3032934509945602)]

Mark points inside with 1 and outside with a 0

select = mesh.select_enclosed_points(rot)

select

Header	Data Arrays
PolyData Information N Cells 3263 N Points 2903 X Bounds -4.446e+00, 5.998e+00 Y Bounds -3.637e+00, 2.760e+00 Z Bounds -1.701e+00, 1.701e+00 N Arrays 1	Name Field Type N Comp Min Max SelectedPoints Points uint8 1 0.000e+00 1.000e+00

Extract two meshes, one completely inside and one completely outside the enclosing surface.

inside = select.threshold(0.5)
outside = select.threshold(0.5, invert=True)

display the results

p = pv.Plotter()
p.add_mesh(outside, color="Crimson", **dargs)
p.add_mesh(inside, color="green", **dargs)
p.add_mesh(rot, color="mintcream", opacity=0.35, **dargs)

p.camera_position = cpos
p.show()

Out:

[(13.0, 7.6, -13.85),
 (0.44, -0.4, -0.37),
 (-0.2830738875949229, 0.9098803529836806, 0.3032934509945602)]