[vtkusers] Clipping DiscreteMarchingCubes extracted object with BoxWidget only clips the front surfaces

[Dieter Rosch]

Good morning,

Apologies for the repost of the question I posted yesterday - when I woke
up this morning I realised I had completely mislabeled the question,
referring to an STL when in fact, the object was a DICOM object I had
extracted using Thresholding and MarchingCubes. Hopefully the clarified
subject line and explanation will target the correct audience.

 I have just started experimenting with VTK via the ActiViz.NET wrapper.
The examples are a very useful introduction to the toolkit.

As an exercise, I have taken the regular BoxWidget example, and replaced
the mace object with an object I have extracted from a DICOM. However I am
running into a slight problem:When I move the BoxWidget to clip the object,
it only seems to clip the front of the object. An example of what I mean is
visible here: <<http://imgur.com/Yalu91C>>. As you can see, only the front
surfaces seem to turn green (green indicates the clipped area).


I am pretty sure it is something small I am missing, it's as if the
clipping algorithm does not see the not clipped part as an outside surface,
perhaps a problem with normals. Can anyone perhaps shed some light on this
for me?.NET Code below for critique,thought it maps pretty closely to the
C++ code:

>
> using Kitware.VTK;
> using System;
>
> /// <summary>
> /// Class containing main method
> /// </summary>
> public class Demo
> {
>
>
>     public static void Main(String[] argv)
>     {
>         string path =
> "C:\\Data\\sandbox\\python\\dicom\\example_images\\Shoulder";
>         var reader = new vtkDICOMImageReader();
>         reader.SetDirectoryName(path);
>
>         var threshold = new vtkImageThreshold();
>         threshold.SetInputConnection(reader.GetOutputPort());
>         threshold.ThresholdByLower(350);// remove all soft tissue
>         threshold.ReplaceInOn();
>         threshold.SetInValue(0);        //set all values below 400 to 0
>         threshold.ReplaceOutOn();
>         threshold.SetOutValue(1);       //set all values above 400 to 1
>
>
>         //Discrete Marching Cubes algorithm
>         var dmc = new vtkDiscreteMarchingCubes();
>         dmc.SetInputConnection(threshold.GetOutputPort());
>         dmc.GenerateValues(1, 1, 1);
>
>         //Clean the mesh
>         var connect = new vtkPolyDataConnectivityFilter();
>         connect.SetInputConnection(dmc.GetOutputPort());
>         connect.SetExtractionModeToLargestRegion();
>
>         var clean = new vtkCleanPolyData();
>         clean.SetInputConnection(connect.GetOutputPort());
>         //clean.SetInputConnection(dmc.GetOutputPort());
>
>         //Smooth
>         var boneSTL = new vtkWindowedSincPolyDataFilter();
>         boneSTL.SetNumberOfIterations(25);
>         boneSTL.SetInputConnection(clean.GetOutputPort());
>
>         glyph = vtkGlyph3D.New();
>
>         glyph.SetInputConnection(boneSTL.GetOutputPort());
>         glyph.SetVectorModeToUseNormal();
>         glyph.SetScaleModeToScaleByVector();
>         glyph.SetScaleFactor(0.25);
>
>         boneMapper = vtkPolyDataMapper.New();
>         boneMapper.SetInputConnection(boneSTL.GetOutputPort());
>
>         boneActor = vtkLODActor.New();
>         boneActor.SetMapper(boneMapper);
>
>         boneActor.VisibilityOn();
>
>         // This portion of the code clips the mace with the vtkPlanes
> implicit function.
>         // The clipped region is colored green.
>         planes = vtkPlanes.New();
>         clipper = vtkClipPolyData.New();
>
>         clipper.SetInputConnection(boneSTL.GetOutputPort());
>         clipper.SetClipFunction(planes);
>         clipper.InsideOutOn();
>
>         selectMapper = vtkPolyDataMapper.New();
>         selectMapper.SetInputConnection(clipper.GetOutputPort());
>         selectMapper.ScalarVisibilityOff();
>
>         selectActor = vtkLODActor.New();
>         selectActor.SetMapper(selectMapper);
>         selectActor.GetProperty().SetColor(0, 1, 0);
>         selectActor.VisibilityOff();
>         selectActor.SetScale(1.01, 1.01, 1.01);
>
>         // Create the RenderWindow, Renderer and both Actors
>         ren1 = vtkRenderer.New();
>         renWin = vtkRenderWindow.New();
>         renWin.AddRenderer(ren1);
>         iren = vtkRenderWindowInteractor.New();
>         iren.SetRenderWindow(renWin);
>
>         // The SetInteractor method is how 3D widgets are associated with
> the render
>         // window interactor. Internally, SetInteractor sets up a bunch of
> callbacks
>         // using the Command/Observer mechanism (AddObserver()).
>         boxWidget = vtkBoxWidget.New();
>         boxWidget.SetInteractor(iren);
>         boxWidget.SetPlaceFactor(1.25);
>         ren1.AddActor(boneActor);
>         ren1.AddActor(selectActor);
>
>         // Add the actors to the renderer, set the background and size
>         ren1.SetBackground(0.1, 0.2, 0.4);
>         renWin.SetSize(600, 600);
>
>         // Place the interactor initially. The input to a 3D widget is
> used to
>         // initially position and scale the widget. The
> EndInteractionEvent is
>         // observed which invokes the SelectPolygons callback.
>         boxWidget.SetInput(glyph.GetOutput());
>         boxWidget.PlaceWidget();
>         boxWidget.EndInteractionEvt += new
> vtkObject.vtkObjectEventHandler(SelectPolygons);
>
>         // render the image
>         iren.Initialize();
>         iren.Start();
>         //Clean up
>         deleteAllVTKObjects();
>     }
>
>     static vtkPolyDataAlgorithm boneSTL;
>     static vtkGlyph3D glyph;
>     static vtkAppendPolyData apd;
>     static vtkPolyDataMapper boneMapper;
>     static vtkLODActor boneActor;
>     static vtkPlanes planes;
>     static vtkClipPolyData clipper;
>     static vtkPolyDataMapper selectMapper;
>     static vtkLODActor selectActor;
>     static vtkRenderer ren1;
>     static vtkRenderWindow renWin;
>     static vtkRenderWindowInteractor iren;
>     static vtkBoxWidget boxWidget;
>
>     /// <summary>
>     /// Callback function for boxWidget.EndInteractionEvt
>     /// </summary>
>     public static void SelectPolygons(vtkObject sender, vtkObjectEventArgs
> e)
>     {
>         boxWidget.GetPlanes(planes);
>         selectActor.VisibilityOn();
>     }
>
>     ///<summary>
>     ///Deletes all static objects created
>     ///</summary>
>     public static void deleteAllVTKObjects()
>     {
>         //clean up vtk objects
>         if (boneSTL != null) { boneSTL.Dispose(); }
>         //if (cone != null) { cone.Dispose(); }
>         if (glyph != null) { glyph.Dispose(); }
>         //if (apd != null) { apd.Dispose(); }
>         if (boneMapper != null) { boneMapper.Dispose(); }
>         if (boneActor != null) { boneActor.Dispose(); }
>         if (planes != null) { planes.Dispose(); }
>         if (clipper != null) { clipper.Dispose(); }
>         if (selectMapper != null) { selectMapper.Dispose(); }
>         if (selectActor != null) { selectActor.Dispose(); }
>         if (ren1 != null) { ren1.Dispose(); }
>         if (renWin != null) { renWin.Dispose(); }
>         if (iren != null) { iren.Dispose(); }
>         if (boxWidget != null) { boxWidget.Dispose(); }
>     }
> }
>
>
> Thank you in advance for the help.
>
> Regards,
> Dieter
>
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