points.rst

Point Data

The vtki.PolyData object adds additional functionality to the vtk.vtkPolyData object, to include direct array access through numpy, one line plotting, and other mesh functions.

PolyData Creation

See :ref:`ref_create_poly` for an example on creating a vtki.PolyData object from NumPy arrays.

Empty Object

A polydata object can be initialized with:

.. testcode:: python

    import vtki
    grid = vtki.PolyData()

This creates an empty grid, and is not useful until points and cells are added to it. VTK points and cells can be added with SetPoints and SetCells, but the inputs to these need to be vtk.vtkCellArray and vtk.vtkPoints objects, which need to be populated with values. Grid creation is simplified by initializing the grid directly from numpy arrays as in the following section.

Initialize from a File

Both binary and ASCII .ply, .stl, and .vtk files can be read using vtki. For example, the vtki package contains example meshes and these can be loaded with:

.. testcode:: python

    import vtki
    from vtki import examples

    # Load mesh
    mesh = vtki.PolyData(examples.planefile)

This mesh can then be written to a vtk file using:

.. testcode:: python

    mesh.save('plane.vtk')

These meshes are identical.

import numpy as np

mesh_from_vtk = vtki.PolyData('plane.vtk')
print(np.allclose(mesh_from_vtk.points, mesh.points))

.. testcleanup:: python

   import os
   try:
       os.remove('plane.vtk')
   except FileNotFoundError:
       pass

Mesh Manipulation and Plotting

Meshes can be directly manipulated using numpy or with the built-in translation and rotation routines. This example loads two meshes and moves, scales, and copies them.

.. testcode:: python

    import vtki
    from vtki import examples

    # load and shrink airplane
    airplane = vtki.PolyData(examples.planefile)
    airplane.points /= 10 # shrink by 10x

    # rotate and translate ant so it is on the plane
    ant = vtki.PolyData(examples.antfile)
    ant.rotate_x(90)
    ant.translate([90, 60, 15])

    # Make a copy and add another ant
    ant_copy = ant.copy()
    ant_copy.translate([30, 0, -10])

To plot more than one mesh a plotting class must be created to manage the plotting. The following code creates the class and plots the meshes with various colors.

.. testcode:: python

    # Create plotting object
    plotter = vtki.Plotter()
    plotter.add_mesh(ant, 'r')
    plotter.add_mesh(ant_copy, 'b')

    # Add airplane mesh and make the color equal to the Y position.  Add a
    # scalar bar associated with this mesh
    plane_scalars = airplane.points[:, 1]
    plotter.add_mesh(airplane, scalars=plane_scalars, stitle='Airplane Y\nLocation')

    # Add annotation text
    plotter.add_text('Ants and Plane Example')
    plotter.plot(screenshot='AntsAndPlane.png')

vtki.PolyData Grid Class Methods

The following is a description of the methods available to a vtki.PolyData object. It inherits all methods from the original vtk object, vtk.vtkPolyData.

Attributes

.. autoautosummary:: vtki.PolyData
   :attributes:

Methods

.. autoautosummary:: vtki.PolyData
   :methods:

.. autoclass:: vtki.PolyData
   :show-inheritance:
   :members:
   :undoc-members: