[vtkusers] Finding neighboring points

[Sara Rolfe]

> Thanks for your reply.  I thought I had done this, but when I  
> checked back I had done so incorrectly, without New().
>
> This fixed my problem :)

On Jan 22, 2011, at 12:25 PM, David Doria wrote:

> Have you created the vtkIdList object before passing it to the  
> function? i.e.
>
> vtkSmartPointer<vtkIdList> connectedVertices =  
> vtkSmartPointer<vtkIdList>::New()
>
> ?
>
> I'm asking this off-list because I believe people sometimes see a
> reply and don't bother to read the original question, and I feel like
> you may need a better response than this!
>
> David
>
>
> On Sat, Jan 22, 2011 at 3:07 PM, Sara Rolfe  
> <smrolfe at u.washington.edu> wrote:
>>
>> Hello,
>> I'm trying to find all the points connected to a vertex point in a  
>> polydata mesh.  I've followed the example here,
>> http://www.vtk.org/Wiki/VTK/Examples/Cxx/PolyData/CellPointNeighbors
>> And the email thread below, which both seem like what I want to do.
>> http://vtk.1045678.n5.nabble.com/Neighbours-of-a-point-in-a-mesh-td1236245.html
>>
>> However, I'm having a problem when I try to use InsertNextId to add  
>> a point to the list of connected points.  I'm getting a bus error  
>> when I get to this line in the code.  Does anyone have an idea  
>> where this might be coming from?  I've checked that the ID I'm  
>> inserting is an int type, and the list is an empty vtkIdList.
>> Thanks,
>> Sara
>> my subroutine to find connected neighbors is below.
>> void GetConnectedVertices(vtkSmartPointer<vtkPolyData> mesh, int  
>> seed, vtkSmartPointer<vtkIdList> connectedVertices)
>> {
>> vtkSmartPointer<vtkIdList> cellIdList =  
>> vtkSmartPointer<vtkIdList>::New(); //get all connected cells
>> mesh->GetPointCells(seed, cellIdList);
>> cout << "Got " << cellIdList->GetNumberOfIds() << " cells using  
>> point " << seed << endl;
>>
>> for(vtkIdType i = 0; i < cellIdList->GetNumberOfIds(); i++){ //  
>> loop through each cell using the seed point
>>
>>
>>
>> cout << "Checking cell " << i << endl;
>> vtkCell* cell = mesh->GetCell(cellIdList->GetId(i)); // get current  
>> cell
>>
>> if(cell->GetNumberOfEdges() <= 0){ //if the cell doesn't have any  
>> edges, it is a line, so skip
>> continue;
>> }
>>
>> for(vtkIdType e = 0; e < cell->GetNumberOfEdges(); e++) // loop  
>> through each edge of the cell
>> {
>> cout << "Checking edge " << e << endl;
>> vtkCell* edge = cell->GetEdge(e); // get current edge
>> vtkIdList* pointIdList = edge->GetPointIds(); // get list of points  
>> on edge
>>
>> if(pointIdList->GetId(0) == seed || pointIdList->GetId(1) ==  
>> seed) // if one of the points on the edge are the vertex point
>> {
>> cout << "Writing connected point" << endl;
>> if(pointIdList->GetId(0) == seed) // if first point on edge is vertex
>> {
>> int temp = pointIdList->GetId(1); // get second point from list
>> cout << "Adding " << temp << " to list" << endl;
>> connectedVertices->InsertNextId(temp); // and insert it into  
>> connected point list
>> }
>> else
>> {
>> int temp = pointIdList->GetId(0); // get second point from list
>> cout << "Adding " << temp << " to list" << endl;
>> connectedVertices->InsertNextId(temp); // else insert first point  
>> into connected point list
>> }
>> }
>> }
>>     }
>> }
>>
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