VTK/Examples/Python/DataManipulation/Cube.py

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This is a transliteration of the C++ example Examples/DataManipulation/Cxx/Cube.cxx in the VTK source distribution.

It illustrates the manual use of vtkPolyData to construct a cube and differs from the Wiki examples VTK/Examples/Python/GeometricObjects/Display/Cube and VTK/Examples/Cxx/GeometricObjects/Cube, which use vtkCube.

Cube.py

#!/usr/bin/env python

# This is (almost) a direct C++ to Python transliteration of
# <VTK-root>/Examples/DataManipulation/Cxx/Cube.cxx from the VTK
# source distribution, which "shows how to manually create vtkPolyData"
#
# A convenience function, mkVtkIdList(), has been added and one if/else
# so the example also works in version 6 or later.
#
# Lines like `obj->Delete()` have been transliterated as `del obj` to,
# preserve the resemblance to the original C++ example, although I 
# doubt this achieves anything beyond what Python's garbage collection
# would do anyway.

import vtk

# Makes a vtkIdList from a Python iterable. I'm kinda surprised that
# this is necessary, since I assumed that this kind of thing would
# have been built into the wrapper and happen transparently, but it
# seems not.
def mkVtkIdList(it):
    vil = vtk.vtkIdList()
    for i in it:
        vil.InsertNextId(int(i))
    return vil


def main():
    # x = array of 8 3-tuples of float representing the vertices of a cube:
    x = [(0.0, 0.0, 0.0), (1.0, 0.0, 0.0), (1.0, 1.0, 0.0), (0.0, 1.0, 0.0),
         (0.0, 0.0, 1.0), (1.0, 0.0 ,1.0), (1.0, 1.0, 1.0), (0.0, 1.0, 1.0)]
    
    # pts = array of 6 4-tuples of vtkIdType (int) representing the faces
    #     of the cube in terms of the above vertices
    pts = [(0,1,2,3), (4,5,6,7), (0,1,5,4),
           (1,2,6,5), (2,3,7,6), (3,0,4,7)]

    # We'll create the building blocks of polydata including data attributes.
    cube    = vtk.vtkPolyData()
    points  = vtk.vtkPoints()
    polys   = vtk.vtkCellArray()
    scalars = vtk.vtkFloatArray()

    # Load the point, cell, and data attributes.
    for i in range(8):
        points.InsertPoint(i, x[i])
    for i in range(6):
        polys.InsertNextCell( mkVtkIdList(pts[i]) )
    for i in range(8):
        scalars.InsertTuple1(i,i)

    # We now assign the pieces to the vtkPolyData.
    cube.SetPoints(points)
    del points
    cube.SetPolys(polys)
    del polys
    cube.GetPointData().SetScalars(scalars)
    del scalars

    # Now we'll look at it.
    cubeMapper = vtk.vtkPolyDataMapper()
    if vtk.VTK_MAJOR_VERSION <= 5:
        cubeMapper.SetInput(cube)
    else:
        cubeMapper.SetInputData(cube)
    cubeMapper.SetScalarRange(0,7)
    cubeActor = vtk.vtkActor()
    cubeActor.SetMapper(cubeMapper)

    # The usual rendering stuff.
    camera = vtk.vtkCamera()
    camera.SetPosition(1,1,1)
    camera.SetFocalPoint(0,0,0)

    renderer = vtk.vtkRenderer()
    renWin   = vtk.vtkRenderWindow()
    renWin.AddRenderer(renderer)

    iren = vtk.vtkRenderWindowInteractor()
    iren.SetRenderWindow(renWin)

    renderer.AddActor(cubeActor)
    renderer.SetActiveCamera(camera)
    renderer.ResetCamera()
    renderer.SetBackground(1,1,1)

    renWin.SetSize(300,300)

    # interact with data
    renWin.Render()
    iren.Start()

    # Clean up
    del cube
    del cubeMapper
    del cubeActor
    del camera
    del renderer
    del renWin
    del iren


main()