problems with vtkContourTriangulator and vtkContourLoopExtration

Support
1

Hello at all,

i have a problem slicing vtkPolyData, and i am stuck there for days now.

I tried the following two pipelines.

first with vtkContourTriangulator:

  1. vtkCleanPolyData

  2. vtkCutter

  3. vtkStripper

  4. vtkContourTriangulator

  5. vtkFeatureEdges

  6. vtkStripper

  7. vtkPolyDataNormals

second with vtkContourLoopExtraction:

  1. vtkCleanPolyData

  2. vtkCutter

  3. vtkStripper

  4. vtkContourLoopExtraction

  5. vtkStripper

  6. vtkPolyDataNormals


  • Problem with the vtkContourTriangulator is, that it produce errors on some layers. Even when changing the tolerance of the vtkCleanPolyData then on other layers errors appear.
    I also looked at the points from the vtkStripper output and they are definitely on the same layer.

stripper_output
stripper_output653Ă—642 17.1 KB

triangulator_out
triangulator_out732Ă—759 51.3 KB

So i dont know what to do? I also could check if the vtkContourTriangulator had an error, if so change the polygon minimal until it didnt has any error, but i dont know if this is a good solution, such an iterative try and error thing…

CPP-File and CMake and vtp-file:
CMakeLists.txt (755 Bytes)
contourTriangulatorTest.cxx (5.6 KB)
bd.vtp (154.0 KB)



CPP-File and CMake and vtp-file:
CMakeLists.txt (830 Bytes)
contourLoopExtractorTest.cxx (5.4 KB)
bd2.vtp (10.1 KB)

Or are there filters which could check the correct winding of a polygon if it is inside another or something like that?

Any help is welcome,

best regards

new pony

2

Hello,
after some more try & error i got the vtkContourTriangulator working in a way, where it is triangulating all my layers.
I want to share my code, even there are probably muuuch better approaches :-).
Steps are:

  • vktCleanPolyData with minimal tolerance
  • vtkCutter with vtkPlane on the layerHeight
  • vtkStripper
  • vtkContourTriangulator
  • check if it has errors
    • if so: rotate around zAxis and triangulate again until no errors or until 360°
      - if rotation > 360° use vtkCleanPolyData again with a higher tolerance
      - rotate and triangulate again => if still errors until rotation > 360 => exception
  • rotate back
  • vtkFeatureEdges

CMakeLists.txt (755 Bytes)
contourTriangulatorTest.cxx (8.7 KB)
bd.vtp (154.0 KB)
PS: the polyData’s 3D file is from Microsoft (Bulldozer.3mf)

regards
philipp

3

Hello,

Some years ago I’ve faced such issues.
I was using vtkClipClosedSurface to make slices of 3D solids, and to display the cut face with some colors.

The way vtkClipClosedSurface works is almost the same as you do :

  1. cut the solids
  2. rebuild closed loops from cut faces
  3. triangulate closed loops

After hours of headache, I found that vtkClipClosedSurface was using vtkContourTriangulator for the 3rd step, and that this tool was far from stable when input geometry was “not simple” (eg. face with many complex holes).

After some more investigations, I solved the problem by replacing vtkContourTriangulator with CDT (GitHub - artem-ogre/CDT: Constrained Delaunay Triangulation (C++)).

1 Like
4

Initial post vtkClipClosedSurface bad result

1 Like