# VTK/Examples/Python/GeometricObjects/Display/Cell3DDemonstration

< VTK‎ | Examples‎ | Python
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## 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.

## Cell3DDemonstration.py

```#!/usr/bin/env python

import vtk

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.Update()

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

def DisplayBodies():

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.SetSize(600, 600)
renWin.SetWindowName('Cell3D Demonstration')

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

# Create one text property for all
textProperty = vtk.vtkTextProperty()
textProperty.SetFontSize(10)
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])

textMappers[i].SetInput(titles[i])
textActors[i].SetMapper(textMappers[i])
textActors[i].SetPosition(50, 10)

gridDimensions = 3
rendererSize = 200

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(.2, .3, .4)
ren.SetViewport(viewport)
continue

renderers[index].SetViewport(viewport)
renderers[index].SetBackground(.2, .3, .4)
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()
return iRen

if __name__ == '__main__':
iRen = DisplayBodies()
#WritePNG(iRen.GetRenderWindow(), "Cell3DDemonstration.png")
iRen.Start()
```