# 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.
    If your VTK version is 5.x then remove the line: colors = vtk.vtkNamedColors()
     and replace the set background parameters with (1.0, 0.9688, 0.8594)

    """

    import vtk

    def mkVtkIdList(it):
        """
        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.

        :param it: A python iterable.
        :return: A vtkIdList
        """
        vil = vtk.vtkIdList()
        for i in it:
            vil.InsertNextId(int(i))
        return vil

    def main():
        colors = vtk.vtkNamedColors()

        # 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, xi in enumerate(x):
            points.InsertPoint(i, xi)
        for pt in pts:
            polys.InsertNextCell(mkVtkIdList(pt))
        for i, _ in enumerate(x):
            scalars.InsertTuple1(i, i)

        # We now assign the pieces to the vtkPolyData.
        cube.SetPoints(points)
        cube.SetPolys(polys)
        cube.GetPointData().SetScalars(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(cube.GetScalarRange())
        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(colors.GetColor3d("Cornsilk"))
        # renderer.SetBackground(1.0, 0.9688, 0.8594)

        renWin.SetSize(600, 600)

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

    if __name__ == "__main__":
        main()