# CellsInsideObject

VTKExamples/Python/PolyData/CellsInsideObject

### Description¶

This example illustrates how to extract the cells that exist inside a closed surface. It uses vtkSelectEnclosedPoints to mark points that are inside and outside the surface. vtkMultiThreshold is used to extract the three meshes into three vtkMultiBlockDataSet's. The cells completely outside are shown in crimson, completely inside are yellow and border cells are green. A translucent copy of the closed surface helps illustrate the selection process.

If two polydata datasets are provided, the example uses the second as the closed surface. If only one dataset is provided, the closed surface is generated by rotating the first dataset by 90 degrees around its Y axis.

Info

The example is run with the cow.g data.

Warning

The surface that contains cells must be closed and manifold. The example does not check for this. Run ClosedSurface (C++) or (Python) to check your surface.

Other Languages

See (Cxx)

Question

### Code¶

CellsInsideObject.py

#!/usr/bin/env python

import vtk

def get_program_parameters():
import argparse
description = 'Read a polydata file of a surface and determine if it is a closed surface.'
epilogue = '''
This example illustrates how to extract the cells that exist inside a closed surface.
It uses vtkSelectEnclosedPoints to mark points that are inside and outside the surface.
vtkMultiThreshold is used to extract the three meshes into three vtkMultiBlockDataSet's.
The cells completely outside are shown in crimson, completely inside are yellow and
border cells are green.
A translucent copy of the closed surface helps illustrate the selection process.

If two polydata datasets are provided, the example uses the second as the closed surface.
If only one dataset is provided, the closed surface is generated by rotating the
first dataset by 90 degrees around its Y axis.

'''
parser = argparse.ArgumentParser(description=description, epilog=epilogue,
formatter_class=argparse.RawDescriptionHelpFormatter)
parser.add_argument('filename1', help='Enter a polydata file e.g cow.g.')
parser.add_argument('filename2', default=None, nargs='?', help='Enter another polydata file e.g cow.g.')
args = parser.parse_args()
return args.filename1, args.filename2

import os
path, extension = os.path.splitext(file_name)
extension = extension.lower()
if extension == ".ply":
elif extension == ".vtp":
elif extension == ".obj":
elif extension == ".stl":
elif extension == ".vtk":
elif extension == ".g":
else:
# Return a None if the extension is unknown.
poly_data = None
return poly_data

def main():
fn1, fn2 = get_program_parameters()
if fn2:
else:
# If only one polydata is present, generate a second polydata by
# rotating the original about its center.
print('Generating modified polyData1')
center = polyData1.GetCenter()
transform = vtk.vtkTransform()
transform.Translate(center[0], center[1], center[2])
transform.RotateY(90.0)
transform.Translate(-center[0], -center[1], -center[2])
transformPD = vtk.vtkTransformPolyDataFilter()
transformPD.SetTransform(transform)
transformPD.SetInputData(polyData1)
transformPD.Update()
polyData2 = transformPD.GetOutput()

# Mark points inside with 1 and outside with a 0
select = vtk.vtkSelectEnclosedPoints()
select.SetInputData(polyData1)
select.SetSurfaceData(polyData2)

# Extract three meshes, one completely inside, one completely
# outside and on the border between the inside and outside.

threshold = vtk.vtkMultiThreshold()
# Outside points have a 0 value in ALL points of a cell
0, 0,
vtk.vtkDataObject.FIELD_ASSOCIATION_POINTS, "SelectedPoints",
0, 1)
# Inside points have a 1 value in ALL points of a cell
1, 1,
vtk.vtkDataObject.FIELD_ASSOCIATION_POINTS, "SelectedPoints",
0, 1)
# Border points have a 0 or a 1 in at least one point of a cell
0, 1,
vtk.vtkMultiThreshold.OPEN, vtk.vtkMultiThreshold.OPEN,
vtk.vtkDataObject.FIELD_ASSOCIATION_POINTS, "SelectedPoints",
0, 0)

threshold.SetInputConnection(select.GetOutputPort())

# Select the intervals to be output
threshold.OutputSet(outsideId)
threshold.OutputSet(insideId)
threshold.OutputSet(borderId)
threshold.Update()

# Visualize
colors = vtk.vtkNamedColors()
outsideColor = colors.GetColor3d("Crimson")
insideColor = colors.GetColor3d("Banana")
borderColor = colors.GetColor3d("Mint")
surfaceColor = colors.GetColor3d("Peacock")
backgroundColor = colors.GetColor3d("Silver")

# Outside
outsideMapper = vtk.vtkDataSetMapper()
outsideMapper.SetInputData(threshold.GetOutput().GetBlock(outsideId).GetBlock(0))
outsideMapper.ScalarVisibilityOff()

outsideActor = vtk.vtkActor()
outsideActor.SetMapper(outsideMapper)
outsideActor.GetProperty().SetDiffuseColor(outsideColor)
outsideActor.GetProperty().SetSpecular(.6)
outsideActor.GetProperty().SetSpecularPower(30)

# Inside
insideMapper = vtk.vtkDataSetMapper()
insideMapper.SetInputData(threshold.GetOutput().GetBlock(insideId).GetBlock(0))
insideMapper.ScalarVisibilityOff()

insideActor = vtk.vtkActor()
insideActor.SetMapper(insideMapper)
insideActor.GetProperty().SetDiffuseColor(insideColor)
insideActor.GetProperty().SetSpecular(.6)
insideActor.GetProperty().SetSpecularPower(30)
insideActor.GetProperty().EdgeVisibilityOn()

# Border
borderMapper = vtk.vtkDataSetMapper()
borderMapper.SetInputData(threshold.GetOutput().GetBlock(borderId).GetBlock(0))
borderMapper.ScalarVisibilityOff()

borderActor = vtk.vtkActor()
borderActor.SetMapper(borderMapper)
borderActor.GetProperty().SetDiffuseColor(borderColor)
borderActor.GetProperty().SetSpecular(.6)
borderActor.GetProperty().SetSpecularPower(30)
borderActor.GetProperty().EdgeVisibilityOn()

surfaceMapper = vtk.vtkDataSetMapper()
surfaceMapper.SetInputData(polyData2)
surfaceMapper.ScalarVisibilityOff()

# Surface of object containing cell
surfaceActor = vtk.vtkActor()
surfaceActor.SetMapper(surfaceMapper)
surfaceActor.GetProperty().SetDiffuseColor(surfaceColor)
surfaceActor.GetProperty().SetOpacity(.1)

renderer = vtk.vtkRenderer()
renderWindow = vtk.vtkRenderWindow()
renderWindow.SetSize(640, 480)

renderWindowInteractor = vtk.vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)

renderer.SetBackground(backgroundColor)
renderer.UseHiddenLineRemovalOn()

renderWindow.SetWindowName('CellsInsideObject')
renderWindow.Render()
renderer.GetActiveCamera().Azimuth(30)
renderer.GetActiveCamera().Elevation(30)
renderer.GetActiveCamera().Dolly(1.25)
renderWindow.Render()

renderWindowInteractor.Start()

if __name__ == '__main__':
main()