# vtkLoopSubdivisionFilter doesn't work properly
**URL:** https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893
**Category:** Support
**Created:** [July 6, 2022, 4:59pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893 "2022-07-06T16:59:48Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@esmitt](https://discourse.vtk.org/u/esmitt)
#### Post date: [July 6, 2022, 4:59pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/1 "2022-07-06T16:59:49Z")
Hello! this is my first post due that I am having a problem:
I am using this example: [https://kitware.github.io/vtk-examples/site/Cxx/Meshes/Subdivision/](https://kitware.github.io/vtk-examples/site/Cxx/Meshes/Subdivision/)
replacing my OBJ file (a simple one based on triangles, vertex, vertex’s normal and faces).
However, the output is as follows:
[Ys4Pw.jpg (1307×678) (imgur.com)](https://i.stack.imgur.com/Ys4Pw.jpg)
Any idea? Thanks!
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### Author:  [@will.schroeder](https://discourse.vtk.org/u/will.schroeder)
#### Post date: [July 6, 2022, 5:17pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/2 "2022-07-06T17:17:47Z")
Is the mesh watertight (manifold)? e.g., no duplicate points or edges, cracks, t-junctions, etc. Some of this can be cleaned up with vtkStaticCleanPolyData / vtkCleanPolyData.
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### Author:  [@esmitt](https://discourse.vtk.org/u/esmitt)
#### Post date: [July 6, 2022, 8:49pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/3 "2022-07-06T20:49:14Z")
Thanks for the answer Will.
I realized that using vtkOBJReader + vtkTriangleFilter, all the triangles are set as separate structures! Then, the image corresponds to a filter applied to each triangle (in a correct way). Thus, my problem is another!
Actually, I set everything to use a polydata P with the following:
GetNumberOfPieces: 1
GetNumberOfPolys: 286598
GetNumberOfPoints: 859794
And, using vtkLoopSubdivisionFilter over P is the image that I attached.
Any clue is welcome
Again, thanks a lot Will
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### Author:  [@will.schroeder](https://discourse.vtk.org/u/will.schroeder)
#### Post date: [July 7, 2022, 11:46am UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/4 "2022-07-07T11:46:11Z")
Can you provide sample data? Assuming the data is triangles (as required by the filter), I am suspicious that the mesh is disconnected in some way.
Another suggestion: use ParaView for quick debugging situations like this. Filters like feature edges can be very helpful in spotting issues.
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### Author:  [@esmitt](https://discourse.vtk.org/u/esmitt)
#### Post date: [July 7, 2022, 5:55pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/5 "2022-07-07T17:55:49Z")
Sure!
Here is a sample OBJ [WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free](https://we.tl/t-QGlGhkr95O) (it expires in 1 week).
Again, thanks.
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### Author:  [@will.schroeder](https://discourse.vtk.org/u/will.schroeder)
#### Post date: [July 7, 2022, 6:46pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/6 "2022-07-07T18:46:02Z")
The triangles are disconnected from each other. Use vtkCleanPolyData or vtkStaticCleanPolyData. This removes duplicate points with the effect of “joining” the mesh polygons.
Also the mesh has non-triangles in it. Finally, there are a few non-manifold edges. Both of which make the subdivision filters unhappy ☹
With a little work the mesh could be cleaned up…
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### Author:  [@esmitt](https://discourse.vtk.org/u/esmitt)
#### Post date: [July 7, 2022, 11:52pm UTC](https://discourse.vtk.org/t/vtkloopsubdivisionfilter-doesnt-work-properly/8893/7 "2022-07-07T23:52:34Z")
I used the vtkStaticCleanPolyData + vtkTriangleFilter with PassLinesOff and PassVertsOff + playing with vtkSmoothPolyDataFilter + vtkPolyDataNormals and I obtained the image.
Isn’t fully subdivided as I expected… but at least is not the mess that I had before ☠
I know that removing the non-manifold points/edges is the way to input in vtk\<…\>SubdivisionFilter but well…is a job for the future me 😬
Will, thanks for the support.
