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Basic API Usage

PyVista provides tools to get started with just about any VTK dataset and wrap that object into an easily accesible data object. Whether you are new to the VTK library or a power user, the best place to get started is with PyVista's :func:`pyvista.wrap` and :func:`vtk.read` functions to either wrap a VTK data object in memory or read a VTK or VTK-friendly file format.

Wrapping a VTK Data Object

The wrapping function is under the :mod:`pyvista.utilities` module which is usable from the top level of PyVista:

import pyvista as pv
wrapped_data = pv.wrap(my_vtk_data_object)

This allows users to quickly wrap any VTK dataset they have to its appropriate PyVista object:

.. testcode:: python

    import vtk
    import pyvista as pv
    stuff = vtk.vtkPolyData()
    better = pv.wrap(stuff)


Reading a VTK File

PyVista provides a convenience function to read VTK file formats into their respective PyVista data objects. Simply call the :func:`pyvista.read` function passing the filename:

import pyvista as pv
data = pv.read('my_strange_vtk_file.vtk')

Accessing the Wrapped Data Object

Now that you have a wrapped VTK data object, you can start accessing and modifying the data! Some of the most common properties to access include the points and point/cell data (the data attributes assigned to the nodes or cells of the mesh respectively).

First, check out some common meta data properties:

.. testcode:: python

    import pyvista as pv
    from pyvista import examples
    import numpy as np

>>> data = examples.load_airplane()
>>> # Inspect how many cells are in this dataset
>>> data.n_cells
2452
>>> # Inspect how many points are in this dataset
>>> data.n_points
1335
>>> # What about scalar arrays? Are there any?
>>> data.n_arrays
0
>>> # What are the data bounds?
>>> data.bounds
[139.06100463867188, 1654.9300537109375, 32.09429931640625, 1319.949951171875, -17.741199493408203, 282.1300048828125]
>>> # Hm, where is the center of this dataset?
>>> data.center
[896.9955291748047, 676.0221252441406, 132.19440269470215]

Access the points by fetching the .points attribute on any PyVista data object as a NumPy array:

>>> the_pts = data.points
>>> isinstance(the_pts, np.ndarray)
True

Accessing the different data attributes on the nodes and cells of the data object is interfaced via dictionaries with callbacks to the VTK object. These dictionaries of the different point and cell arrays can be directly accessed and modified as NumPy arrays. In the example below, we load a dataset, access an array on that dataset, then add some more data:

>>> data = examples.load_uniform()
>>> # Fetch a data array from the point data dictionary
>>> arr = data.point_arrays['Spatial Point Data']
>>> # Assign a new array to the cell data:
>>> data.cell_arrays['foo'] = np.random.rand(data.n_cells)
>>> # Don't remember if your array is point or cell data? Doesn't matter!
>>> foo = data['foo']
>>> isinstance(foo, np.ndarray)
True
>>> # Or maybe you just want to add an array where it fits
>>> data['new-array'] = np.random.rand(data.n_points)

Plotting

PyVista includes numerous plotting routines that are intended to be intuitive and highly controllable with matplotlib similar syntax and keyword arguments. To get started, try out the :func:`pyvista.plot` convenience method that is binded to each PyVista data object:

.. testcode:: python

    import pyvista as pv
    from pyvista import examples

    data = examples.load_airplane()
    data.plot(screenshot='airplane.png')


../images/auto-generated/airplane.png

You can also create the plotter to highly control the scene. First, instantiate a plotter such as :class:`pyvista.Plotter` or :class:`pyvista.BackgroundPlotter`:

The :class:`pyvista.Plotter` will create a rendering window that will pause the execution of the code after calling show.

.. testcode:: python

    plotter = pv.Plotter()  # instantiate the plotter
    plotter.add_mesh(data)    # add a dataset to the scene
    cpos = plotter.show()     # show the rendering window


Note that the show method will return the last used camera position of the rendering window incase you want to chose a camera position and use it agian later.

You can then use this cached camera for additional plotting without having to manually interact with the plotting window:

plotter = pv.Plotter(off_screen=True)
plotter.add_mesh(data, color='tan')
plotter.camera_position = cpos
plotter.show(screenshot='airplane.png')

Be sure to check out all the available plotters for your use case:

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