# Cube

VTKExamples/Python/DataManipulation/Cube

### Description

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 Cube and Cube, which use vtkCube.

### Code

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()