[vtkusers] Missing Neighbors in VTKPolyData
Bill Lorensen
bill.lorensen at gmail.com
Mon Dec 2 11:13:36 EST 2013
If the edges are coincident, you can run CleanPolyData.
On Mon, Dec 2, 2013 at 11:15 AM, Martin Klemm
<martin.klemm at hs-offenburg.de> wrote:
> Thank you. vtkFeatureEdges shows me exactly the edges that return just 2
> neighbors instead of three. But do you know any way to resolve this issue?
> How can I connect this edges with its proper neighbors?
>
>
> On 02.12.2013 16:36, Bill Lorensen wrote:
>>
>> The filter vtkFeatureEdges can detect boundary edges. See this example:
>> http://vtk.org/Wiki/VTK/Examples/Cxx/Meshes/BoundaryEdges
>>
>>
>> On Mon, Dec 2, 2013 at 9:12 AM, Martin Klemm
>> <martin.klemm at hs-offenburg.de> wrote:
>>>
>>> The surface was generated by the vtkPowerCrustSurfaceFilter (found here
>>> http://www.sq3.org.uk/powercrust/ ). Since I need triangles I used a
>>> trianglefilter afterwards. Then I used a vtkFillHolesFilter in case there
>>> is
>>> a hole (but I think it is not necessary). Then I use two planes to clip
>>> away
>>> a part of the generated surface. Because vtkClipClosedSurface can produce
>>> lines I used another triangle filter to filter out the lines.
>>>
>>> And the problem happens with the output of the last triangle filter. So
>>> my
>>> pipeline is as follows:
>>> vtkPowerCrustSurfaceFilter -> vtkTriangleFilter -> vtkFillHolesFilter ->
>>> vtkClipClosedSurface -> vtkTriangleFilter
>>>
>>> Do you know how I can check for cracks in the surface? Or is there even a
>>> good way to close them?
>>>
>>> Thanks for your help!
>>>
>>>
>>>
>>> On 02.12.2013 14:27, Bill Lorensen wrote:
>>>>
>>>>
>>>> How was the surface generated. Perhaps there are cracks in the surface.
>>>>
>>>>
>>>> On Mon, Dec 2, 2013 at 2:33 AM, Martin Klemm
>>>> <martin.klemm at hs-offenburg.de> wrote:
>>>>>
>>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>> I am currently working on a function that passes through all cells of a
>>>>> triangulated power crust surface. Depending on the normal of the cell
>>>>> it
>>>>> is
>>>>> classified as valid or invalid. The algorithm works except of a problem
>>>>> that
>>>>> occurs in certain cells.
>>>>>
>>>>> For my algorithm I use GetCellEdgeNeighbors of vtkPolyData to receive
>>>>> the
>>>>> edge neighbors of a cell. On a closed surface there should be three
>>>>> neighbors for a triangle. However, some triangles just have two
>>>>> neighbors.
>>>>>
>>>>> Then I checked the point neighbors which shows the same result. There
>>>>> are
>>>>> no
>>>>> coincident neighbors on this "weird" edge.
>>>>>
>>>>> Then I rendered the neighbors and the current cell as you can see here:
>>>>>
>>>>> http://www.picamatic.com/view/9881191_Unbenannt/
>>>>>
>>>>> Moreover I print the point neighbors:
>>>>> curCell = 719
>>>>> point neighbors first point: 719 1151 1153
>>>>> point neighbors second point: 714 715 719 721 722 7
>>>>> point neighbors third point: 719 720 721 1151 1152
>>>>>
>>>>> It looks like that even there are neighbors they are not linked to each
>>>>> other. And it seems like there are more neighbors than the renderwindow
>>>>> really shows. Could that be because there are really small triangles
>>>>> that
>>>>> you cannot really see in the renderer? Do you have any suggestions how
>>>>> to
>>>>> improve this situation?
>>>>>
>>>>> And here is my function to get the neighbors of a specified cell:
>>>>>
>>>>>
>>>>> /**
>>>>> * \brief Gets the neighbors of a specified cell (triangle)
>>>>> * \param inputTriangles The input cells (triangles)
>>>>> * \param cellId The specified ID of the cell
>>>>> * \param neighbors A list with the neighbors of the specified cell
>>>>> *
>>>>> * \warning You have to call vtkTriangleFilter before using this
>>>>> function.
>>>>> * \todo Figure out how it is possible that on a closed surface a
>>>>> triangle
>>>>> can have less than three
>>>>> * neighbors.
>>>>> */
>>>>> void SurfaceReconstructScreen::GetCellNeighbors(vtkPolyData*
>>>>> inputTriangles,
>>>>> vtkIdType cellId,
>>>>> QList<vtkIdType>&
>>>>> neighbors,
>>>>> bool debug)
>>>>> {
>>>>> //clear result list
>>>>> neighbors.clear();
>>>>>
>>>>> //build links in order to use getcellneighbors
>>>>> inputTriangles->BuildLinks();
>>>>>
>>>>> //
>>>>> vtkSmartPointer<vtkIdList> cellPointIds =
>>>>> vtkSmartPointer<vtkIdList>::New();
>>>>> inputTriangles->GetCellPoints(cellId, cellPointIds);
>>>>>
>>>>> for(vtkIdType i = 0; i < cellPointIds->GetNumberOfIds(); i++)
>>>>> {
>>>>> vtkSmartPointer<vtkIdList> idList =
>>>>> vtkSmartPointer<vtkIdList>::New();
>>>>> vtkIdType firstPoint;
>>>>> vtkIdType secondPoint;
>>>>>
>>>>> //add one of the edge points
>>>>> firstPoint = cellPointIds->GetId(i);
>>>>>
>>>>> //add the other edge point
>>>>> if(i+1 == cellPointIds->GetNumberOfIds())
>>>>> {
>>>>> secondPoint = cellPointIds->GetId(0);
>>>>> }
>>>>> else
>>>>> {
>>>>> secondPoint = cellPointIds->GetId(i + 1);
>>>>> }
>>>>>
>>>>> //get the neighbors of the cell
>>>>> vtkSmartPointer<vtkIdList> neighborCellIds =
>>>>> vtkSmartPointer<vtkIdList>::New();
>>>>>
>>>>> inputTriangles->GetCellEdgeNeighbors(cellId, firstPoint,
>>>>> secondPoint,
>>>>> neighborCellIds);
>>>>>
>>>>> for(vtkIdType j = 0; j < neighborCellIds->GetNumberOfIds();
>>>>> j++)
>>>>> {
>>>>> neighbors.push_back(neighborCellIds->GetId(j));
>>>>> }
>>>>> }
>>>>> }
>>>>>
>>>>>
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>>
>
> --
>
>
> Martin Klemm
> Hochschule Offenburg
> Badstraße 24
> 77652 Offenburg
> Tel. +49 781 / 205 - 4681
--
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