[vtkusers] clip one vtkPolyData with another?

[Alle Meije Wink]

Hi David and others,

Thanks for your many hints and tips. I tried vtkSelectPolyData,
vtkStencil, and vtkImplicitLoop, but at the moment nothing works.

(the subdivision thing did not work, because the triangles of the cut
surface -the clipcow way- differed orders of magnitude in size)

>>I can't see how I should do this. From the test code for
>>vtkImplicitSelectionLoop I saw that you can use it to extract a piece of
>>a surface (such as the isosurface), but what I would need is a piece of
>>the cut-plane
> 
> I was thinking you would cut your isosurface to get a polyline (after a
> pass through vtkStripper?). This polyline would be the 'loop' which is then
> used to clip the cut planes with vtkImplicitSelectionLoop.

My script is below, the (MRI) data is still at www.wbic.cam.ac.uk/~amw71

I thought that this code would clip the cut surface, i.e. remove the
part of the cut surface outside the brain iso-surface (defined by
isoNormals).

Instead, the cut surface still extends outside the brain (to the extent
of the bounding box). There are cuts out of the cut surface *inside* the
brain. I have captured the latest result in
http://www.wbic.cam.ac.uk/~amw71/SurfaceCut3.png

(grey value tresholded:http://www.wbic.cam.ac.uk/~amw71/SurfaceCut.png,
 plain clipped plane:  http://www.wbic.cam.ac.uk/~amw71/SurfaceCut2.png)

I am still trying to find a way to show the cut planes with the grey
values inside, but with the planes cut so that only the part inside the
surface is shown.

Does this output make any sense (to anybody)?

Thanks!
Alle Meije



attached: script to  show isosurface and saggital cut-plane
===========================================================



############################################################
# Prepare the GUI

catch {load vtktcl}
source vtkInt.tcl
source colors.tcl

############################################################
# Load the brain data

vtkImageReader anatomyReader
  anatomyReader SetFileName "BrainTemplate.vtk"
  anatomyReader SetFileDimensionality 3
  anatomyReader SetHeaderSize 215
  anatomyReader SetDataSpacing 1 1 1
  anatomyReader SetDataExtent 0 90 0 108 0 90
  anatomyReader SetDataScalarTypeToUnsignedChar

############################################################
# generate the isosurface from the ICBM template

vtkMarchingCubes BrainIso
  BrainIso SetInput [anatomyReader GetOutput]
  BrainIso SetValue 0 70

vtkSmoothPolyDataFilter smooth
  smooth SetInput [BrainIso GetOutput]
  smooth SetNumberOfIterations 20

vtkTriangleFilter triangulate
  triangulate SetInput [smooth GetOutput]

############################################################
# clip the brain

vtkPoints points
  points InsertPoint 0 50.3 58.0 36.0
  points InsertPoint 1 50.3 58.0 36.0
  points InsertPoint 2 50.3 58.0 36.0

vtkFloatArray normals
  normals SetNumberOfComponents 3
  normals SetNumberOfTuples 3
  normals SetTuple3 0  1.0   0.0  0.0
  normals SetTuple3 1  0.0  -1.0  0.0
  normals SetTuple3 2  0.0   0.0 -1.0

vtkPlanes clipplanes
  clipplanes SetPoints points
  clipplanes SetNormals normals

vtkClipPolyData clipper
  clipper SetInput [triangulate GetOutput]
  clipper SetClipFunction clipplanes

vtkPolyDataMapper BrainIsoMapper
  BrainIsoMapper SetInput [clipper GetOutput]
  BrainIsoMapper ScalarVisibilityOff

vtkActor BrainIsoActor
  BrainIsoActor SetMapper BrainIsoMapper
  eval [BrainIsoActor GetProperty] SetColor .6 .3 .3
  eval [BrainIsoActor GetProperty] SetOpacity 1

# set origins at centres of volumes

BrainIsoActor SetOrigin 46 55 46

############################################################
# generate the slices at the clipping position

############################################################
# cutplane: Sag

# cut the volume (make cut-plane with grey values)
vtkPlane planeSag
  planeSag SetOrigin 50.3 58.0 36.0
  planeSag SetNormal -1 0 0

vtkCutter cutSag
  cutSag SetInput [anatomyReader GetOutput]
  cutSag SetCutFunction planeSag

# cut the isosurface (make a contour+normals of the cut)

vtkPolyDataNormals isoNormals
  isoNormals SetInput [smooth GetOutput]

vtkCutter cutEdgesSag;
  cutEdgesSag SetInput [isoNormals GetOutput]
  cutEdgesSag SetCutFunction planeSag

vtkStripper cutStripsSag;
  cutStripsSag SetInput [cutEdgesSag GetOutput]
  cutStripsSag Update

vtkImplicitSelectionLoop cutLoopSag
  cutLoopSag SetLoop [[cutEdgesSag GetOutput] GetPoints]

vtkClipPolyData clippedCutSag
  clippedCutSag SetInput [cutSag GetOutput]
  clippedCutSag SetClipFunction cutLoopSag

# make the actor for the saggittal cutplane
 vtkPolyDataMapper cutPlaneMapperSag
   cutPlaneMapperSag SetInput [clippedCutSag GetOutput]
 vtkActor actorSag
   actorSag SetMapper cutPlaneMapperSag

############################################################
# Create the RenderWindow, Renderer and add Actors

# Create the camera

vtkCamera camera
  camera SetFocalPoint   46  55  46
  camera SetPosition    -80 -40 -50
  camera Azimuth 180
  camera Roll 270

# add the actors

vtkRenderer renWindow
  renWindow SetActiveCamera camera
  renWindow AddActor BrainIsoActor
  renWindow AddActor actorSag

  renWindow SetBackground .5 .5 .5

# Use the camera in the renderwindow

vtkRenderWindow renWin
  renWin AddRenderer renWindow
  renWin SetSize 512 512

vtkRenderWindowInteractor RenderControl
  RenderControl SetRenderWindow renWin
  RenderControl Initialize

############################################################

# Define custom interaction.

vtkRenderWindowInteractor iren
  iren SetInteractorStyle ""
  iren SetRenderWindow renWin
  iren AddObserver KeyPressEvent Keypress

############################################################
# write out files in other formats

file delete -force Cover.wrl

vtkVRMLExporter vrml
vrml SetInput renWin
vrml SetFileName Cover.wrl
vrml Write

# prevent the tk window from showing up, then start the event loop

wm withdraw .



		
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