Helpers

Helpers#

The pyvista module contains several functions to simplify the creation and manipulation of meshes or interfacing with VTK datasets.

Wrap a VTK Dataset#

helpers.wrap() → pyvista.DataSet | pyvista.pyvista_ndarray | None[source]#

Wrap any given VTK data object to its appropriate PyVista data object.

Other formats that are supported include:

Changed in version 0.38.0: If the passed object is already a wrapped PyVista object, then this is no-op and will return that object directly. In previous versions of PyVista, this would perform a shallow copy.

Parameters:
datasetnumpy.ndarray | trimesh.Trimesh | vtk.DataSet

Dataset to wrap.

Returns:
pyvista.DataSet

The PyVista wrapped dataset.

Examples

Wrap a numpy array representing a random point cloud.

>>> import numpy as np
>>> import pyvista as pv
>>> points = np.random.default_rng().random((10, 3))
>>> cloud = pv.wrap(points)
>>> cloud
PolyData (...)
  N Cells:    10
  N Points:   10
  N Strips:   0
  X Bounds:   ...
  Y Bounds:   ...
  Z Bounds:   ...
  N Arrays:   0

Wrap a VTK object.

>>> import pyvista as pv
>>> import vtk
>>> points = vtk.vtkPoints()
>>> p = [1.0, 2.0, 3.0]
>>> vertices = vtk.vtkCellArray()
>>> pid = points.InsertNextPoint(p)
>>> _ = vertices.InsertNextCell(1)
>>> _ = vertices.InsertCellPoint(pid)
>>> point = vtk.vtkPolyData()
>>> _ = point.SetPoints(points)
>>> _ = point.SetVerts(vertices)
>>> mesh = pv.wrap(point)
>>> mesh
PolyData (...)
  N Cells:    1
  N Points:   1
  N Strips:   0
  X Bounds:   1.000e+00, 1.000e+00
  Y Bounds:   2.000e+00, 2.000e+00
  Z Bounds:   3.000e+00, 3.000e+00
  N Arrays:   0

Wrap a Trimesh object.

>>> import trimesh
>>> import pyvista as pv
>>> points = [[0, 0, 0], [0, 0, 1], [0, 1, 0]]
>>> faces = [[0, 1, 2]]
>>> tmesh = trimesh.Trimesh(points, faces=faces, process=False)
>>> mesh = pv.wrap(tmesh)
>>> mesh  
PolyData (0x7fc55ff27ad0)
  N Cells:  1
  N Points: 3
  X Bounds: 0.000e+00, 0.000e+00
  Y Bounds: 0.000e+00, 1.000e+00
  Z Bounds: 0.000e+00, 1.000e+00
  N Arrays: 0

Simplified Triangular Mesh Construction#

points.make_tri_mesh(faces)[source]#

Construct a pyvista.PolyData mesh using points and faces arrays.

Construct a mesh from an Nx3 array of points and an Mx3 array of triangle indices, resulting in a mesh with N vertices and M triangles. This function does not require the standard VTK “padding” column and simplifies mesh creation.

Parameters:
pointsnp.ndarray

Array of points with shape (N, 3) storing the vertices of the triangle mesh.

facesnp.ndarray

Array of indices with shape (M, 3) containing the triangle indices.

Returns:
pyvista.PolyData

PolyData instance containing the triangle mesh.

Examples

This example discretizes the unit square into a triangle mesh with nine vertices and eight faces.

>>> import numpy as np
>>> import pyvista as pv
>>> points = np.array(
...     [
...         [0, 0, 0],
...         [0.5, 0, 0],
...         [1, 0, 0],
...         [0, 0.5, 0],
...         [0.5, 0.5, 0],
...         [1, 0.5, 0],
...         [0, 1, 0],
...         [0.5, 1, 0],
...         [1, 1, 0],
...     ]
... )
>>> faces = np.array(
...     [
...         [0, 1, 4],
...         [4, 7, 6],
...         [2, 5, 4],
...         [4, 5, 8],
...         [0, 4, 3],
...         [3, 4, 6],
...         [1, 2, 4],
...         [4, 8, 7],
...     ]
... )
>>> tri_mesh = pv.make_tri_mesh(points, faces)
>>> tri_mesh.plot(show_edges=True, line_width=5)
../../_images/helpers-2_00_00.png

Lines from Points#

points.lines_from_points(close: bool = False)[source]#

Make a connected line set given an array of points.

Parameters:
pointsarray_like[float]

Points representing the vertices of the connected segments. For example, two line segments would be represented as np.array([[0, 0, 0], [1, 0, 0], [1, 1, 0]]).

closebool, default: False

If True, close the line segments into a loop.

Returns:
pyvista.PolyData

PolyData with lines and cells.

Examples

>>> import numpy as np
>>> import pyvista as pv
>>> points = np.array([[0, 0, 0], [1, 0, 0], [1, 1, 0]])
>>> poly = pv.lines_from_points(points)
>>> poly.plot(line_width=5)
../../_images/helpers-3_00_00.png

Line Segments from Points#

points.line_segments_from_points()[source]#

Generate non-connected line segments from points.

Assumes points are ordered as line segments and an even number of points.

Parameters:
pointsarray_like[float]

Points representing line segments. An even number must be given as every two vertices represent a single line segment. For example, two line segments would be represented as np.array([[0, 0, 0], [1, 0, 0], [1, 0, 0], [1, 1, 0]]).

Returns:
pyvista.PolyData

PolyData with lines and cells.

Examples

This example plots two line segments at right angles to each other.

>>> import pyvista as pv
>>> import numpy as np
>>> points = np.array([[0, 0, 0], [1, 0, 0], [1, 0, 0], [1, 1, 0]])
>>> lines = pv.line_segments_from_points(points)
>>> lines.plot()
../../_images/helpers-4_00_00.png

Convert to and from VTK Data Types#

arrays.convert_array(name=None, deep: bool = False, array_type=None)[source]#

Convert a NumPy array to a vtkDataArray or vice versa.

Parameters:
arrnp.ndarray | vtkDataArray

A numpy array or vtkDataArry to convert.

namestr, optional

The name of the data array for VTK.

deepbool, default: False

If input is numpy array then deep copy values.

array_typeint, optional

VTK array type ID as specified in vtkType.h.

Returns:
vtkDataArray or numpy.ndarray

The converted array. If input is a numpy.ndarray then returns vtkDataArray or is input is vtkDataArray then returns NumPy ndarray.

Fit Plane to Points#

points.fit_plane_to_points(return_meta: bool = False, resolution=10, init_normal=None)[source]#

Fit a plane to points using its principal_axes().

The plane is automatically sized and oriented to fit the extents of the points.

Changed in version 0.42.0: The generated plane is now sized and oriented to match the points.

Changed in version 0.42.0: The center of the plane (returned if return_meta=True) is now computed as the center of the generated plane mesh. In previous versions, the center of the input points was returned.

Changed in version 0.45.0: The internal method used for fitting the plane has changed. Previously, singular value decomposition (SVD) was used, but eigenvectors are now used instead. See warning below.

Warning

The sign of the plane’s normal vector prior to version 0.45 may differ from the latest version. This may impact methods which rely on the plane’s direction. Use init_normal to control the sign explicitly.

Parameters:
pointsarray_like[float]

Size [N x 3] sequence of points to fit a plane through.

return_metabool, default: False

If True, also returns the center and normal of the generated plane.

resolutionint, default: 10

Number of points on the plane mesh along its edges. Specify two numbers to set the resolution along the plane’s long and short edge (respectively) or a single number to set both edges to have the same resolution.

Added in version 0.45.0.

init_normalVectorLike[float] | str, optional

Flip the normal of the plane such that it best aligns with this vector. Can be a vector or string specifying the axis by name (e.g. 'x' or '-x', etc.).

Added in version 0.45.0.

Returns:
pyvista.PolyData

Plane mesh.

pyvista.pyvista_ndarray

Plane center if return_meta=True.

pyvista.pyvista_ndarray

Plane normal if return_meta=True.

See also

fit_line_to_points

Fit a line using the first principal axis of the points.

principal_axes

Compute axes vectors which best fit a set of points.

Examples

Fit a plane to a random point cloud.

>>> import pyvista as pv
>>> import numpy as np
>>> from pyvista import examples
>>>
>>> rng = np.random.default_rng(seed=0)
>>> cloud = rng.random((10, 3))
>>> cloud[:, 2] *= 0.1
>>>
>>> plane = pv.fit_plane_to_points(cloud)

Plot the point cloud and fitted plane.

>>> pl = pv.Plotter()
>>> _ = pl.add_mesh(plane, style='wireframe', line_width=4)
>>> _ = pl.add_points(
...     cloud,
...     render_points_as_spheres=True,
...     color='r',
...     point_size=30,
... )
>>> pl.show()
../../_images/helpers-5_00_00.png

Fit a plane to a mesh and return its metadata. Set the plane resolution to 1 so that the plane has no internal points or edges.

>>> mesh = examples.download_shark()
>>> plane, center, normal = pv.fit_plane_to_points(
...     mesh.points, return_meta=True, resolution=1
... )

Plot the mesh and fitted plane.

>>> pl = pv.Plotter()
>>> _ = pl.add_mesh(plane, show_edges=True, opacity=0.25)
>>> _ = pl.add_mesh(mesh, color='gray')
>>> pl.camera_position = [
...     (-117, 76, 235),
...     (1.69, -1.38, 0),
...     (0.189, 0.957, -0.22),
... ]
>>> pl.show()
../../_images/helpers-5_01_00.png

Use the metadata with pyvista.DataSetFilter.clip() to split the mesh into two.

>>> first_half, second_half = mesh.clip(
...     origin=center, normal=normal, return_clipped=True
... )

Plot the two halves of the clipped mesh.

>>> pl = pv.Plotter()
>>> _ = pl.add_mesh(first_half, color='red')
>>> _ = pl.add_mesh(second_half, color='blue')
>>> pl.camera_position = [
...     (-143, 43, 40),
...     (-8.7, -11, -14),
...     (0.25, 0.92, -0.29),
... ]
>>> pl.show()
../../_images/helpers-5_02_00.png

Note that it is pointing in the positive z-direction.

>>> normal
pyvista_ndarray([5.2734075e-09, 6.7008443e-08, 1.0000000e+00],
                dtype=float32)

Use init_normal to flip the sign and make it negative instead.

>>> _, _, normal = pv.fit_plane_to_points(
...     mesh.points, return_meta=True, init_normal='-z'
... )
>>> normal
pyvista_ndarray([-5.2734155e-09, -6.7008422e-08, -1.0000000e+00],
                dtype=float32)

Fit Line to Points#

points.fit_line_to_points(
*,
resolution: int = 1,
init_direction: VectorLike[float] | None = None,
return_meta: bool = False,
)[source]#

Fit a line to points using its principal_axes().

The line is automatically sized and oriented to fit the extents of the points.

Added in version 0.45.0.

Parameters:
pointsMatrixLike[float]

Size [N x 3] array of points to fit a line through.

resolutionint, default: 1

Number of pieces to divide the line into.

init_directionVectorLike[float], optional

Flip the direction of the line’s points such that it best aligns with this vector. Can be a vector or string specifying the axis by name (e.g. 'x' or '-x', etc.).

return_metabool, default: False

If True, also returns the length (magnitude) and direction of the line.

Returns:
pyvista.PolyData

Line mesh.

float

Line length if return_meta=True.

numpy.ndarray

Line direction (unit vector) if return_meta=True.

See also

fit_plane_to_points

Fit a plane using the first two principal axes of the points.

principal_axes

Compute axes vectors which best fit a set of points.

Examples

Download a point cloud. The points trace a path along topographical surface.

>>> import pyvista as pv
>>> from pyvista import examples
>>> mesh = examples.download_gpr_path()

Fit a line to the points and plot the result. The line of best fit is colored red.

>>> line = pv.fit_line_to_points(mesh.points)

>>> pl = pv.Plotter()
>>> _ = pl.add_mesh(mesh, color='black', line_width=10)
>>> _ = pl.add_mesh(line, color='red', line_width=5)
>>> pl.show()
../../_images/helpers-6_00_00.png

Fit a line to a mesh and return the metadata.

>>> mesh = examples.download_human()
>>> line, length, direction = pv.fit_line_to_points(
...     mesh.points, return_meta=True
... )

Show the length of the line.

>>> length
167.6145387467733

Plot the line as an arrow to show its direction.

>>> arrow = pv.Arrow(
...     start=line.points[0],
...     direction=direction,
...     scale=length,
...     tip_length=0.2,
...     tip_radius=0.04,
...     shaft_radius=0.01,
... )

>>> pl = pv.Plotter()
>>> _ = pl.add_mesh(mesh, opacity=0.5)
>>> _ = pl.add_mesh(arrow, color='red')
>>> pl.show()
../../_images/helpers-6_01_00.png

Set init_direction to the positive z-axis to flip the line’s direction.

>>> mesh = examples.download_human()
>>> line, length, direction = pv.fit_line_to_points(
...     mesh.points, init_direction='z', return_meta=True
... )

Plot the results again with an arrow.

>>> arrow = pv.Arrow(
...     start=line.points[0],
...     direction=direction,
...     scale=length,
...     tip_length=0.2,
...     tip_radius=0.04,
...     shaft_radius=0.01,
... )

>>> pl = pv.Plotter()
>>> _ = pl.add_mesh(mesh, opacity=0.5)
>>> _ = pl.add_mesh(arrow, color='red')
>>> pl.show()
../../_images/helpers-6_02_00.png