[vtkusers] Re: vtkOBBTree vs. vtkCellLocator

[Goodwin Lawlor]

No, nothing in vtkOBBTree can do that... you'd have to write the function yourself. Perhaps vtkDataSet::FindCell does what you want (its a superclass of vtkUnstructuredGrid).

HTH

Goodwin
University College Dublin
  ----- Original Message ----- 
  From: M. Campopiano 
  To: goodwin.lawlor at ucd.ie ; vtkusers at vtk.org 
  Sent: Monday, November 17, 2003 10:22 PM
  Subject: Re: vtkOBBTree vs. vtkCellLocator


  Thanks for the response, Goodwin.. 

  So is there any function at all in OBBTree that I can use to locate which cell contains any pariticular point in an unstructured grid..?

  (and anywyas - I think CellLocator is apparantly more effecient right?)
  Thanks
  Mike

  >From: "Goodwin Lawlor" 
  >Reply-To: "Goodwin Lawlor" 
  >To: "VTK-User" , 
  >Subject: vtkOBBTree vs. vtkCellLocator 
  >Date: Mon, 17 Nov 2003 20:56:35 -0000 
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  > 
  >Hi Mike, 
  > 
  >You could use vtkGeometryFilter to convert your ugrid to polydata and set 
  >this as the dataset in vtkOBBTree. This isn't the end of your problems- 
  >FindClosestPoint will crash anyway from vtkOBBTree. 
  > 
  >The problem occurs because vtkCellLocator defines "vtkIdList **Tree" whereas 
  >vtkOBBTree defines "vtkOBBNode *Tree". FindClosestPoint() expects "vtkIdList 
  >**Tree" and crashes in GetBucketNeighbours() when it doesn't get it from a 
  >vtkOBBTree object. 
  > 
  >Basically, FindClosestPoint is for use only with vtkCellLocator... if you 
  >want to uses it with vtkOBBTree you'd have to add a FindClosestPoint method 
  >to that class (which uses the vtkOBBNode data structure). 
  > 
  >HTH 
  > 
  >Goodwin 
  >University College Dublin 
  > 
  > > From: "M. Campopiano" 
  > > To: vtkusers at vtk.org 
  > > Date: Fri, 14 Nov 2003 18:20:09 +0000 
  > > Subject: [vtkusers] vtkOBBTree vs. vtkCellLocator 
  > > 
  > > Hello again, 
  > > 
  > > So I was able to use vtkCellLocator using the following: 
  > > 
  > > celllocator->SetDataSet(ugrid); 
  > > celllocator->BuildLocator(); 
  > > celllocator->FindClosestPoint(x, closestpoint, cellid, subid, dist); 
  > > 
  > > And now I invoke the EXACT same methods with vtkOBBTree but it crashes at 
  > > BuildLocator()..????? 
  > > 
  > > obbtree->SetDataSet(ugrid); 
  > > obbtree->BuildLocator(); //CRASHES HERE!!!!!!!!!!!!!????? 
  > > obbtree->FindClosestPoint(xobb, closestpointobb, cellidobb, subidobb, 
  > > distobb); 
  > > 
  > > Can anyone tell me why it works for the CellLocator and not for the 
  > > OBBTree?? Its the exact same thing.. Note that my unstructured grid 
  >contains 
  > > quadratic tetra's 
  > > 
  > > Thanks 
  > > Mike 
  > 


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