[vtkusers] clip one vtkPolyData with another?

[David.Pont at ensisjv.com]

Alle Meije Wink <alle_meije at yahoo.co.uk> wrote on 27/02/2006 09:13:31:

Well Alle Meije I am running out of ideas, especially as I have never
worked with volume data.
You might want to take a look at Slicer (www.slicer.org), maybe the people
over there have some ideas?

   regards
   Dave P

> 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 .
>
>
>
>
> ___________________________________________________________
> To help you stay safe and secure online, we've developed the all new
> Yahoo! Security Centre. http://uk.security.yahoo.com