Introduction to VTK + Python

1. The VTK pipeline

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VTK pipeline example in Python

A simple example of a vtk pipeline in Python. This pipeline renders a red cube within an interactive vtkRenderWindow (basic interaction controlls --zoom, pan, rotate-- are enabled via the vtkRenderWindowInteractor). In this case we use the vtkCubeSource which generates the basic description of a cube (vertices and cells --or faces--). Other typical sources/primitives provided by vtk are: vtkConeSource, vtkSphereSource, and vtkArrowSource among others.

__Further exploration:__ Go to the vtk online documentation and check which other sources are available! here

2. Creating your own pipeline



In [1]:

    
import vtk



In [2]:

    
# create a rendering window and renderer
renderer = vtk.vtkRenderer()
renderer.SetBackground(0.5, 1.0, 0.5)

renderWindow = vtk.vtkRenderWindow()
renderWindow.SetSize(500, 500)
renderWindow.AddRenderer(renderer)
renderWindow.Render()



In [2]:

    
# create a data source
cube = vtk.vtkCubeSource()

# mapper
cubeMapper = vtk.vtkPolyDataMapper()
cubeMapper.SetInputConnection(cube.GetOutputPort())

# actor
cubeActor = vtk.vtkActor()
cubeActor.SetMapper(cubeMapper)
cubeActor.GetProperty().SetColor(1, 0, 0)

# create a rendering window and renderer
renderer = vtk.vtkRenderer()
renderer.SetBackground(0.5, 0.5, 0.5)
renderer.AddActor(cubeActor)

renderWindow = vtk.vtkRenderWindow()
renderWindow.SetSize(500, 500)
renderWindow.AddRenderer(renderer)
renderWindow.Render()

# create and enable a renderWindowInteractor
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renderWindow)
iren.Start()

3. VTK Data Objects

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A closer look to a VTK file (ASCII)

Polygonal data

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Unstructured data

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__Task:__ Go ahead and open in a text editor the files exercise_op1.vtk and exercise_op2.vtk. These are two different approaches to represent the unstructured grid displayed above using different cell types.

VTK-viewer module for Jupyter Notebook



In [4]:

    
#Source: https://gitlab.com/colonel_zentor/vtk-viewer

%gui qt
import vtk
from vtkviewer import SimpleVtkViewer, create_test_actor

vtkSourceSphere = vtk.vtkSphereSource()
vtkSourceSphere.SetCenter(0.0, 0.0, 0.0)
vtkSourceSphere.SetRadius(10.0)
vtkSourceSphere.SetPhiResolution(60)
vtkSourceSphere.SetThetaResolution(60)

vtkMapperSphere = vtk.vtkPolyDataMapper()
vtkMapperSphere.SetInputConnection(vtkSourceSphere.GetOutputPort())

vtkActorSphere = vtk.vtkActor()
vtkActorSphere.SetMapper(vtkMapperSphere)
vtkActorSphere.GetProperty().SetColor(1.0, 0.0, 0.0)

vtkSimpleWin = SimpleVtkViewer()
vtkSimpleWin.add_actor(vtkActorSphere)
vtkSimpleWin.hide_axes()



In [5]:

    
vtkActorSphere.GetProperty().SetColor(1.0, 1.0, 0.0)



In [6]:

    
vtkActorSphere.GetProperty().SetRepresentationToWireframe()



In [7]:

    
vtkSimpleWin.clear_view()



In [8]:

    
vtkSimpleWin.add_actor(vtkActorSphere)

__Further exploration:__ Notebook example using this module here __Task:__ Use this module to build the pipeline in section 2 stepwise, try changing parameters, sources, etc.

Embedding VTK Renders in Jupyter Notebook



In [3]:

    
# Original source: http://nbviewer.jupyter.org/gist/certik/5723420
# An explained version of this code: https://pyscience.wordpress.com/2014/09/03/ipython-notebook-vtk/

import vtk
from IPython.display import Image
def vtk_show(renderer, width=400, height=300):
    """
    Takes vtkRenderer instance and returns an IPython Image with the rendering.
    """
    renderWindow = vtk.vtkRenderWindow()
    renderWindow.SetOffScreenRendering(1)
    renderWindow.AddRenderer(renderer)
    renderWindow.SetSize(width, height)
    renderWindow.Render()
     
    windowToImageFilter = vtk.vtkWindowToImageFilter()
    windowToImageFilter.SetInput(renderWindow)
    windowToImageFilter.Update()
     
    writer = vtk.vtkPNGWriter()
    writer.SetWriteToMemory(1)
    writer.SetInputConnection(windowToImageFilter.GetOutputPort())
    writer.Write()
    data = bytes(memoryview(writer.GetResult()))
    
    return Image(data)

vtkSourceSphere = vtk.vtkSphereSource()
vtkSourceSphere.SetCenter(0.0, 0.0, 0.0)
vtkSourceSphere.SetRadius(10.0)
vtkSourceSphere.SetPhiResolution(10)
vtkSourceSphere.SetThetaResolution(10)

vtkMapperSphere = vtk.vtkPolyDataMapper()
vtkMapperSphere.SetInputConnection(vtkSourceSphere.GetOutputPort())

vtkActorSphere = vtk.vtkActor()
vtkActorSphere.SetMapper(vtkMapperSphere)
vtkActorSphere.GetProperty().SetColor(1.0, 0.0, 0.0)

vtkRenderer = vtk.vtkRenderer()
vtkRenderer.SetBackground(1.0, 1.0, 1.0)
vtkRenderer.AddActor(vtkActorSphere)

vtk_show(vtkRenderer, width=500, height=500)









    Out[3]:



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