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# Cell3DDemonstration

VTKEx/Python/GeometricObjects/Cell3DDemonstration

### Description

This is a demonstration of how to construct and display geometric objects using the classes derived from vtkCell3D. For each object we specify the points and cell Ids.

From this we create an unstructured grid. In some cases a vtkCellArray is used and the result is added to the unstructured grid, see: MakePolyhedron() and MakeTetrahedron().

Also demonstrated is the use of vectors to hold the unstructured grids, mappers, actors and renderers.

The resultant objects are then displayed in a grid.

Other languages

See (Cxx)

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### Code

Cell3DDemonstration.py

    #!/usr/bin/env python

    import vtk

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

        # Set the background color.
        colors.SetColor("BkgColor", [51, 77, 102, 255])

        titles = list()
        textMappers = list()
        textActors = list()

        uGrids = list()
        mappers = list()
        actors = list()
        renderers = list()

        uGrids.append(MakeHexagonalPrism())
        titles.append('Hexagonal Prism')
        uGrids.append(MakeHexahedron())
        titles.append('Hexahedron')
        uGrids.append(MakePentagonalPrism())
        titles.append('Pentagonal Prism')

        uGrids.append(MakePolyhedron())
        titles.append('Polyhedron')
        uGrids.append(MakePyramid())
        titles.append('Pyramid')
        uGrids.append(MakeTetrahedron())
        titles.append('Tetrahedron')

        uGrids.append(MakeVoxel())
        titles.append('Voxel')
        uGrids.append(MakeWedge())
        titles.append('Wedge')

        renWin = vtk.vtkRenderWindow()
        renWin.SetWindowName('Cell3D Demonstration')

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

        # Create one text property for all
        textProperty = vtk.vtkTextProperty()
        textProperty.SetFontSize(16)
        textProperty.SetJustificationToCentered()

        # Create and link the mappers actors and renderers together.
        for i in range(0, len(uGrids)):
            textMappers.append(vtk.vtkTextMapper())
            textActors.append(vtk.vtkActor2D())

            mappers.append(vtk.vtkDataSetMapper())
            actors.append(vtk.vtkActor())
            renderers.append(vtk.vtkRenderer())

            mappers[i].SetInputData(uGrids[i])
            actors[i].SetMapper(mappers[i])
            actors[i].GetProperty().SetColor(
                colors.GetColor3d("Seashell"))
            renderers[i].AddViewProp(actors[i])

            textMappers[i].SetInput(titles[i])
            textMappers[i].SetTextProperty(textProperty)

            textActors[i].SetMapper(textMappers[i])
            textActors[i].SetPosition(120, 16)
            renderers[i].AddViewProp(textActors[i])

            renWin.AddRenderer(renderers[i])

        gridDimensions = 3
        rendererSize = 300

        renWin.SetSize(rendererSize * gridDimensions,
                       rendererSize * gridDimensions)

        for row in range(0, gridDimensions):
            for col in range(0, gridDimensions):
                index = row * gridDimensions + col

                # (xmin, ymin, xmax, ymax)
                viewport = [
                    float(col) * rendererSize /
                    (gridDimensions * rendererSize),
                    float(gridDimensions - (row + 1)) * rendererSize /
                    (gridDimensions * rendererSize),
                    float(col + 1) * rendererSize /
                    (gridDimensions * rendererSize),
                    float(gridDimensions - row) * rendererSize /
                    (gridDimensions * rendererSize)]

                if index > len(actors) - 1:
                    # Add a renderer even if there is no actor.
                    # This makes the render window background all the same color.
                    ren = vtk.vtkRenderer()
                    ren.SetBackground(colors.GetColor3d("BkgColor"))
                    ren.SetViewport(viewport)
                    renWin.AddRenderer(ren)
                    continue

                renderers[index].SetViewport(viewport)
                renderers[index].SetBackground(colors.GetColor3d("BkgColor"))
                renderers[index].ResetCamera()
                renderers[index].GetActiveCamera().Azimuth(30)
                renderers[index].GetActiveCamera().Elevation(-30)
                renderers[index].GetActiveCamera().Zoom(0.85)
                renderers[index].ResetCameraClippingRange()

        iRen.Initialize()
        renWin.Render()
        iRen.Start()

    def MakeHexagonalPrism():
        """
          3D: hexagonal prism: a wedge with an hexagonal base.
          Be careful, the base face ordering is different from wedge.
        """

        numberOfVertices = 12

        points = vtk.vtkPoints()

        points.InsertNextPoint(0.0, 0.0, 1.0)
        points.InsertNextPoint(1.0, 0.0, 1.0)
        points.InsertNextPoint(1.5, 0.5, 1.0)
        points.InsertNextPoint(1.0, 1.0, 1.0)
        points.InsertNextPoint(0.0, 1.0, 1.0)
        points.InsertNextPoint(-0.5, 0.5, 1.0)

        points.InsertNextPoint(0.0, 0.0, 0.0)
        points.InsertNextPoint(1.0, 0.0, 0.0)
        points.InsertNextPoint(1.5, 0.5, 0.0)
        points.InsertNextPoint(1.0, 1.0, 0.0)
        points.InsertNextPoint(0.0, 1.0, 0.0)
        points.InsertNextPoint(-0.5, 0.5, 0.0)

        hexagonalPrism = vtk.vtkHexagonalPrism()
        for i in range(0, numberOfVertices):
            hexagonalPrism.GetPointIds().SetId(i, i)

        ug = vtk.vtkUnstructuredGrid()
        ug.InsertNextCell(hexagonalPrism.GetCellType(),
                          hexagonalPrism.GetPointIds())
        ug.SetPoints(points)

        return ug

    def MakeHexahedron():
        """
          A regular hexagon (cube) with all faces square and three squares around
           each vertex is created below.

          Setup the coordinates of eight points
           (the two faces must be in counter clockwise
           order as viewed from the outside).

          As an exercise you can modify the coordinates of the points to create
           seven topologically distinct convex hexahedras.
        """
        numberOfVertices = 8

        # Create the points
        points = vtk.vtkPoints()
        points.InsertNextPoint(0.0, 0.0, 0.0)
        points.InsertNextPoint(1.0, 0.0, 0.0)
        points.InsertNextPoint(1.0, 1.0, 0.0)
        points.InsertNextPoint(0.0, 1.0, 0.0)
        points.InsertNextPoint(0.0, 0.0, 1.0)
        points.InsertNextPoint(1.0, 0.0, 1.0)
        points.InsertNextPoint(1.0, 1.0, 1.0)
        points.InsertNextPoint(0.0, 1.0, 1.0)

        # Create a hexahedron from the points
        hex_ = vtk.vtkHexahedron()
        for i in range(0, numberOfVertices):
            hex_.GetPointIds().SetId(i, i)

        # Add the points and hexahedron to an unstructured grid
        uGrid = vtk.vtkUnstructuredGrid()
        uGrid.SetPoints(points)
        uGrid.InsertNextCell(hex_.GetCellType(), hex_.GetPointIds())

        return uGrid

    def MakePentagonalPrism():
        numberOfVertices = 10

        # Create the points
        points = vtk.vtkPoints()
        points.InsertNextPoint(11, 10, 10)
        points.InsertNextPoint(13, 10, 10)
        points.InsertNextPoint(14, 12, 10)
        points.InsertNextPoint(12, 14, 10)
        points.InsertNextPoint(10, 12, 10)
        points.InsertNextPoint(11, 10, 14)
        points.InsertNextPoint(13, 10, 14)
        points.InsertNextPoint(14, 12, 14)
        points.InsertNextPoint(12, 14, 14)
        points.InsertNextPoint(10, 12, 14)

        # Pentagonal Prism
        pentagonalPrism = vtk.vtkPentagonalPrism()
        for i in range(0, numberOfVertices):
            pentagonalPrism.GetPointIds().SetId(i, i)

        # Add the points and hexahedron to an unstructured grid
        uGrid = vtk.vtkUnstructuredGrid()
        uGrid.SetPoints(points)
        uGrid.InsertNextCell(pentagonalPrism.GetCellType(),
                             pentagonalPrism.GetPointIds())

        return uGrid

    def MakePolyhedron():
        """
          Make a regular dodecahedron. It consists of twelve regular pentagonal
          faces with three faces meeting at each vertex.
        """
        # numberOfVertices = 20
        numberOfFaces = 12
        # numberOfFaceVertices = 5

        points = vtk.vtkPoints()
        points.InsertNextPoint(1.21412, 0, 1.58931)
        points.InsertNextPoint(0.375185, 1.1547, 1.58931)
        points.InsertNextPoint(-0.982247, 0.713644, 1.58931)
        points.InsertNextPoint(-0.982247, -0.713644, 1.58931)
        points.InsertNextPoint(0.375185, -1.1547, 1.58931)
        points.InsertNextPoint(1.96449, 0, 0.375185)
        points.InsertNextPoint(0.607062, 1.86835, 0.375185)
        points.InsertNextPoint(-1.58931, 1.1547, 0.375185)
        points.InsertNextPoint(-1.58931, -1.1547, 0.375185)
        points.InsertNextPoint(0.607062, -1.86835, 0.375185)
        points.InsertNextPoint(1.58931, 1.1547, -0.375185)
        points.InsertNextPoint(-0.607062, 1.86835, -0.375185)
        points.InsertNextPoint(-1.96449, 0, -0.375185)
        points.InsertNextPoint(-0.607062, -1.86835, -0.375185)
        points.InsertNextPoint(1.58931, -1.1547, -0.375185)
        points.InsertNextPoint(0.982247, 0.713644, -1.58931)
        points.InsertNextPoint(-0.375185, 1.1547, -1.58931)
        points.InsertNextPoint(-1.21412, 0, -1.58931)
        points.InsertNextPoint(-0.375185, -1.1547, -1.58931)
        points.InsertNextPoint(0.982247, -0.713644, -1.58931)

        # Dimensions are [numberOfFaces][numberOfFaceVertices]
        dodechedronFace = [
            [0, 1, 2, 3, 4],
            [0, 5, 10, 6, 1],
            [1, 6, 11, 7, 2],
            [2, 7, 12, 8, 3],
            [3, 8, 13, 9, 4],
            [4, 9, 14, 5, 0],
            [15, 10, 5, 14, 19],
            [16, 11, 6, 10, 15],
            [17, 12, 7, 11, 16],
            [18, 13, 8, 12, 17],
            [19, 14, 9, 13, 18],
            [19, 18, 17, 16, 15]
        ]

        dodechedronFacesIdList = vtk.vtkIdList()
        # Number faces that make up the cell.
        dodechedronFacesIdList.InsertNextId(numberOfFaces)
        for face in dodechedronFace:
            # Number of points in the face == numberOfFaceVertices
            dodechedronFacesIdList.InsertNextId(len(face))
            # Insert the pointIds for that face.
            [dodechedronFacesIdList.InsertNextId(i) for i in face]

        uGrid = vtk.vtkUnstructuredGrid()
        uGrid.InsertNextCell(vtk.VTK_POLYHEDRON, dodechedronFacesIdList)
        uGrid.SetPoints(points)

        return uGrid

    def MakePyramid():
        """
          Make a regular square pyramid.
        """
        numberOfVertices = 5

        points = vtk.vtkPoints()

        p = [
            [1.0, 1.0, 0.0],
            [-1.0, 1.0, 0.0],
            [-1.0, -1.0, 0.0],
            [1.0, -1.0, 0.0],
            [0.0, 0.0, 1.0]
        ]
        for pt in p:
            points.InsertNextPoint(pt)

        pyramid = vtk.vtkPyramid()
        for i in range(0, numberOfVertices):
            pyramid.GetPointIds().SetId(i, i)

        ug = vtk.vtkUnstructuredGrid()
        ug.SetPoints(points)
        ug.InsertNextCell(pyramid.GetCellType(), pyramid.GetPointIds())

        return ug

    def MakeTetrahedron():
        """
          Make a tetrahedron.
        """
        numberOfVertices = 4

        points = vtk.vtkPoints()
        points.InsertNextPoint(0, 0, 0)
        points.InsertNextPoint(1, 0, 0)
        points.InsertNextPoint(1, 1, 0)
        points.InsertNextPoint(0, 1, 1)

        tetra = vtk.vtkTetra()
        for i in range(0, numberOfVertices):
            tetra.GetPointIds().SetId(i, i)

        cellArray = vtk.vtkCellArray()
        cellArray.InsertNextCell(tetra)

        unstructuredGrid = vtk.vtkUnstructuredGrid()
        unstructuredGrid.SetPoints(points)
        unstructuredGrid.SetCells(vtk.VTK_TETRA, cellArray)

        return unstructuredGrid

    def MakeVoxel():
        """
          A voxel is a representation of a regular grid in 3-D space.
        """
        numberOfVertices = 8

        points = vtk.vtkPoints()
        points.InsertNextPoint(0, 0, 0)
        points.InsertNextPoint(1, 0, 0)
        points.InsertNextPoint(0, 1, 0)
        points.InsertNextPoint(1, 1, 0)
        points.InsertNextPoint(0, 0, 1)
        points.InsertNextPoint(1, 0, 1)
        points.InsertNextPoint(0, 1, 1)
        points.InsertNextPoint(1, 1, 1)

        voxel = vtk.vtkVoxel()
        for i in range(0, numberOfVertices):
            voxel.GetPointIds().SetId(i, i)

        ug = vtk.vtkUnstructuredGrid()
        ug.SetPoints(points)
        ug.InsertNextCell(voxel.GetCellType(), voxel.GetPointIds())

        return ug

    def MakeWedge():
        """
          A wedge consists of two triangular ends and three rectangular faces.
        """

        numberOfVertices = 6

        points = vtk.vtkPoints()

        points.InsertNextPoint(0, 1, 0)
        points.InsertNextPoint(0, 0, 0)
        points.InsertNextPoint(0, .5, .5)
        points.InsertNextPoint(1, 1, 0)
        points.InsertNextPoint(1, 0.0, 0.0)
        points.InsertNextPoint(1, .5, .5)

        wedge = vtk.vtkWedge()
        for i in range(0, numberOfVertices):
            wedge.GetPointIds().SetId(i, i)

        ug = vtk.vtkUnstructuredGrid()
        ug.SetPoints(points)
        ug.InsertNextCell(wedge.GetCellType(), wedge.GetPointIds())

        return ug

    def WritePNG(renWin, fn, magnification=1):
        """
          Screenshot

          Write out a png corresponding to the render window.

          :param: renWin - the render window.
          :param: fn - the file name.
          :param: magnification - the magnification.
        """
        windowToImageFilter = vtk.vtkWindowToImageFilter()
        windowToImageFilter.SetInput(renWin)
        windowToImageFilter.SetMagnification(magnification)
        # Record the alpha (transparency) channel
        # windowToImageFilter.SetInputBufferTypeToRGBA()
        windowToImageFilter.SetInputBufferTypeToRGB()
        # Read from the back buffer
        windowToImageFilter.ReadFrontBufferOff()
        windowToImageFilter.Update()

        writer = vtk.vtkPNGWriter()
        writer.SetFileName(fn)
        writer.SetInputConnection(windowToImageFilter.GetOutputPort())
        writer.Write()

    if __name__ == '__main__':
        main()