Basic API Usage

PyVista provides tools to get started with just about any VTK dataset and wrap that object into an easily accessible data object. Whether you are new to the VTK library or a power user, the best place to get started is with PyVista’s pyvista.wrap() and pyvista.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 pyvista.utilities module which is usable from the top level of PyVista. This allows users to quickly wrap any VTK dataset they have as a PyVista object:

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 pyvista.read() function passing the filename:

import pyvista as pv
mesh = 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 dataset! 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-properties:

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

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

>>> the_pts = mesh.points
>>> isinstance(the_pts, np.ndarray)
True
>>> the_pts[0:5, :]
array([[896.994 ,  48.7601,  82.2656],
       [906.593 ,  48.7601,  80.7452],
       [907.539 ,  55.4902,  83.6581],
       [896.994 ,  55.4902,  85.3283],
       [896.994 ,  42.8477,  77.825 ]], dtype=float32)

Accessing the different data attributes on the nodes and cells of the mesh 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:

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

import pyvista as pv
from pyvista import examples

mesh = examples.load_airplane()
mesh.plot(screenshot='airplane.png')
../_images/airplane.png

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

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

plotter = pv.Plotter()    # instantiate the plotter
plotter.add_mesh(mesh)    # add a mesh 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 in case you want to chose a camera position and use it again 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(mesh, color='tan')
plotter.camera_position = cpos
plotter.show(screenshot='airplane.png')

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