# EllipticalCylinderDemo

VTKExamples/Python/GeometricObjects/EllipticalCylinderDemo

### Description¶

The example shows the vtkPolyLine that forms the base of the elliptical cylinder and an oriented arrow that represents the vector that vtkLinearExtrusionFilter uses to create the cylinder. The example takes an optional triple that defines the vector for the filter. The length of the vector is the height of the cylinder.

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### Code¶

EllipticalCylinderDemo.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import math

import vtk

def main():
nx, ny, nz = get_program_parameters()
colors = vtk.vtkNamedColors()

angle = 0
r1 = 50
r2 = 30
centerX = 10.0
centerY = 5.0

points = vtk.vtkPoints()
idx = 0
while angle <= 2.0 * vtk.vtkMath.Pi() + (vtk.vtkMath.Pi() / 60.0):
points.InsertNextPoint(r1 * math.cos(angle) + centerX,
r2 * math.sin(angle) + centerY,
0.0)
angle = angle + (vtk.vtkMath.Pi() / 60.0)
idx += 1

line = vtk.vtkPolyLine()
line.GetPointIds().SetNumberOfIds(idx)
for i in range(0, idx):
line.GetPointIds().SetId(i, i)

lines = vtk.vtkCellArray()
lines.InsertNextCell(line)

polyData = vtk.vtkPolyData()
polyData.SetPoints(points)
polyData.SetLines(lines)

extrude = vtk.vtkLinearExtrusionFilter()
extrude.SetInputData(polyData)
extrude.SetExtrusionTypeToNormalExtrusion()
extrude.SetVector(nx, ny, nz)
extrude.Update()

# Create an oriented arrow
startPoint = [0.0] * 3
endPoint = [0.0] * 3
startPoint[0] = centerX
startPoint[1] = centerY
startPoint[2] = 0.0
endPoint[0] = startPoint[0] + extrude.GetVector()[0]
endPoint[1] = startPoint[1] + extrude.GetVector()[1]
endPoint[2] = startPoint[2] + extrude.GetVector()[2]

# Compute a basis
normalizedX = [0.0] * 3
normalizedY = [0.0] * 3
normalizedZ = [0.0] * 3

# The X axis is a vector from start to end
vtk.vtkMath.Subtract(endPoint, startPoint, normalizedX)
length = vtk.vtkMath.Norm(normalizedX)
vtk.vtkMath.Normalize(normalizedX)

# The Z axis is an arbitrary vector cross X
arbitrary = [0.0] * 3
arbitrary[0] = vtk.vtkMath.Random(-10, 10)
arbitrary[1] = vtk.vtkMath.Random(-10, 10)
arbitrary[2] = vtk.vtkMath.Random(-10, 10)
vtk.vtkMath.Cross(normalizedX, arbitrary, normalizedZ)
vtk.vtkMath.Normalize(normalizedZ)

# The Y axis is Z cross X
vtk.vtkMath.Cross(normalizedZ, normalizedX, normalizedY)
matrix = vtk.vtkMatrix4x4()

# Create the direction cosine matrix
matrix.Identity()
for i in range(0, 3):
matrix.SetElement(i, 0, normalizedX[i])
matrix.SetElement(i, 1, normalizedY[i])
matrix.SetElement(i, 2, normalizedZ[i])

# Apply the transforms
transform = vtk.vtkTransform()
transform.Translate(startPoint)
transform.Concatenate(matrix)
transform.Scale(length, length, length)

arrowSource = vtk.vtkArrowSource()
arrowSource.SetTipResolution(31)
arrowSource.SetShaftResolution(21)

# Transform the polydata
transformPD = vtk.vtkTransformPolyDataFilter()
transformPD.SetTransform(transform)
transformPD.SetInputConnection(arrowSource.GetOutputPort())

# Create a mapper and actor for the arrow
arrowMapper = vtk.vtkPolyDataMapper()
arrowMapper.SetInputConnection(transformPD.GetOutputPort())

arrowActor = vtk.vtkActor()
arrowActor.SetMapper(arrowMapper)
arrowActor.GetProperty().SetColor(colors.GetColor3d("Tomato"))

tubes = vtk.vtkTubeFilter()
tubes.SetInputData(polyData)
tubes.SetNumberOfSides(21)

lineMapper = vtk.vtkPolyDataMapper()
lineMapper.SetInputConnection(tubes.GetOutputPort())

lineActor = vtk.vtkActor()
lineActor.SetMapper(lineMapper)
lineActor.GetProperty().SetColor(colors.GetColor3d("Peacock"))

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputConnection(extrude.GetOutputPort())

actor = vtk.vtkActor()
actor.SetMapper(mapper)
actor.GetProperty().SetColor(colors.GetColor3d("Banana"))
actor.GetProperty().SetOpacity(.7)

ren = vtk.vtkRenderer()
ren.SetBackground(colors.GetColor3d("SlateGray"))

renWin = vtk.vtkRenderWindow()
renWin.SetWindowName("Elliptical Cylinder Demo")
renWin.SetSize(600, 600)

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

style = vtk.vtkInteractorStyleTrackballCamera()
iren.SetInteractorStyle(style)

camera = vtk.vtkCamera()
camera.SetPosition(0, 1, 0)
camera.SetFocalPoint(0, 0, 0)
camera.SetViewUp(0, 0, 1)
camera.Azimuth(30)
camera.Elevation(30)

ren.SetActiveCamera(camera)
ren.ResetCamera()
ren.ResetCameraClippingRange()

renWin.Render()
iren.Start()

def get_program_parameters():
import argparse
description = 'Elliptical Cylinder Demo.'
epilogue = '''
The example shows the vtkPolyLine that forms the base of the elliptical cylinder
and an oriented arrow that represents the vector that vtkLinearExtrusionFilter
uses to create the cylinder.
The example takes an optional triple that defines the vector for the filter.
The length of the vector is the height of the cylinder.
'''
parser = argparse.ArgumentParser(description=description, epilog=epilogue,
formatter_class=argparse.RawDescriptionHelpFormatter)