[Insight-developers] Join vertex on QEMeshes

Thu Jun 26 12:10:48 EDT 2008

Alex,

in release mode everything seems to be fine, but in debug I am getting
the 0 for nopoint...

Find the output below.

  Best,

    Thomas

$ /cygdrive/d/devel/QEMeshTests/bin/release/JoinVertexTest.exe smallMesh.vtk ou
tput.vtk 0 1
QETriangleMeshType::m_NoPoint: 1410065407
QETriangleMeshType::m_NoFace: 1410065407
# points before:        16
# edges before: 42
# faces before: 28
Deleting point: 0...done.
# points after: 15
# edges after:  39
# faces after:  26
82 GenerateData

boetthw3 at EH40OO2C /cygdrive/d/Images/MeshCreation
$ /cygdrive/d/devel/QEMeshTests/bin/debug/JoinVertexTest.exe smallMesh.vtk outp
ut.vtk 0 1
QETriangleMeshType::m_NoPoint: 0
QETriangleMeshType::m_NoFace: 0
# points before:        16
# edges before: 42
# faces before: 28
Deleting point: 0...done.
# points after: 16
# edges after:  42
# faces after:  28
82 GenerateData

On Thu, Jun 26, 2008 at 2:35 PM, Alexandre GOUAILLARD
<Alexandre_Gouaillard at hms.harvard.edu> wrote:
> Hi thomas,
>
> M_NoPoint is defined as vcl_numeric_limits< OriginRefType >::max()
> In itkGeometricalQuadEdge.txx
> It should not be 0.
>
> I never met this case, I will to make a code that deletes the cell #0
> (should always be an edge BTW) and see what happen.
>
> Thanks,
>
> Alex.
>
> On 6/26/08 8:08 AM, "Thomas Boettger" <tboettger at googlemail.com> wrote:
>
>> Alex,
>>
>> one more thing:
>>
>> I found the following lines of code which do worry me a little bit:
>>
>> itkQuadEdgeMesh::LightWeightDeleteEdge(...) (around Line 900)
>>
>>   CellIdentifier LineIdent = e->GetIdent( );
>>   if( LineIdent != m_NoPoint )
>>     {
>>     EdgeCellType* edgeCell = dynamic_cast< EdgeCellType* >(
>> this->GetCells( )->GetElement( LineIdent ) );
>>     this->LightWeightDeleteEdge( edgeCell );
>>     }
>>   else
>>     {
>>     itkDebugMacro( "Edge Not found. LineIdent not set?" );
>>     return;
>>     }
>>
>> Here you compare the LineIdentifier to m_NoPoint. In my version
>> m_NoPoint is defined as 0. For the very first edge
>> FindFirstUnusedCellIndex() will return 0 as well.
>>
>> Then I cannot delete the edge added first. This will of course stop
>> the JoinVertex function from working for this first edge. The edge is
>> not deleted and then the point is not isolated and cannot be deleted.
>>
>> Is this problem know already? May be you can use
>>
>>   NumericTraits<unsigned long>::max()
>>
>> instead ?
>>
>> In my own decimation I unfortunately always tried to join the vertices
>> of this first edge and was wondering why the point count was not
>> decreasing.
>>
>>
>>   Best regards,
>>
>>     Thomas
>>
>>
>>
>> On Thu, Jun 26, 2008 at 11:07 AM, Thomas Boettger
>> <tboettger at googlemail.com> wrote:
>>> Hi Alex,
>>>
>>> thanks for the quick response. I will test this. The decimation
>>> framework sounds interesting. I would be great if I would be able to
>>> implement my own decimation criteria based on you new code.
>>>
>>> Did you also discuss changes for the SimplexMesh classes. I think the
>>> mesh class could could almost be discarded, but I guess ITK wants to
>>> keep it for backwards compatibility. The deformation filter itself is
>>> rather simple as long as you can access each points three neighbors
>>> (which is quite simple with the QEmeshes we should be fine. One open
>>> issue is where we should store all the computed values like the
>>> barycentric coordinates, normals and so on. This currently is quite
>>> messy in the old code.
>>>
>>> I also never really used the contributed classes as I continued
>>> developing and changing loads of small things in the deformable model
>>> itself, e.g. multi threading, global contraints based on ICP (by
>>> incorporating vtk classes), different external force computations and
>>> more...
>>>
>>> So I cannot really tell what the best way would be for future
>>> directions. But I am willing to discuss, help and maybe contribute if
>>> I can be of any help.
>>>
>>>
>>>  Best,
>>>
>>>    Thomas
>>>
>>>
>>> On Wed, Jun 25, 2008 at 10:55 PM, Alexandre GOUAILLARD
>>> <Alexandre_Gouaillard at hms.harvard.edu> wrote:
>>>> Hi thomas.
>>>>
>>>> Problem solved.
>>>> It was indeed because of the points IDs.
>>>> I added a method to QEMesh that you should call before you write the mesh"
>>>> SqueezePointsIds()
>>>>
>>>> I added this one line in your code and it works fine (it was thus a
>>>> vizualization problem.
>>>>
>>>> BTW we have a decimation code ready, and we are going to put it in ITK
>>>> beofre the end of the week. It's a complete framework, where you can plug
>>>> the stop criterion and so on.
>>>> We have a dedicated priorty queue for mesh decimation, a decimation engine
>>>> (based on JoinVErtex, indeed), an edgelength criterion, and we are polishing
>>>> a Quadratic criterion right now.
>>>>
>>>> Alex.
>>>>
>>>>
>>>> On 6/25/08 12:01 PM, "Thomas Boettger" <tboettger at googlemail.com> wrote:
>>>>
>>>>> ---------- Forwarded message ----------
>>>>> From: Thomas Boettger <tboettger at googlemail.com>
>>>>> Date: Wed, Jun 25, 2008 at 5:59 PM
>>>>> Subject: Join vertex on QEMeshes
>>>>> To: alex Gouaillard <AGouaillard at slb.com>, baghdadi at sickkids.ca
>>>>>
>>>>>
>>>>> Hi Alex and Leila,
>>>>>
>>>>> I started experimenting with the QEMesh classes (ITK 3.6.0).
>>>>>
>>>>> And ran into the following problem:
>>>>>
>>>>> 1. I load a vtk mesh
>>>>> 2. Call JoinVertexFunction for an arbitrary edge (look through the
>>>>> input vtk file in a text editor and choose one line.
>>>>> 3. Store the mesh
>>>>>
>>>>> I expected to see a correct output mesh (with one point less and all
>>>>> edges and faces correct), but when I load both, input and result to
>>>>> paraview the result looks corrupted.
>>>>>
>>>>> You can use the source code in the attached zip file to reproduce it.
>>>>> Just ignore all lines of code besides the main function...
>>>>>
>>>>> I also attach you the mesh I used for the testing (smallMesh.vtk) and
>>>>> the result (result.vtk).
>>>>>
>>>>> cmd line inputs were:
>>>>> $ /cygdrive/d/devel/QEMeshTests/bin/release/JoinVertexTest.exe
>>>>> smallMesh.vtk result.vtk 0 3
>>>>>
>>>>> I am not sure what is going wrong. Maybe I did not understand the
>>>>> JoinVertex operator and need to take care of face corrections myself
>>>>> after deleting the point?
>>>>>
>>>>> Help is welcome...
>>>>>
>>>>>
>>>>>  Best regards,
>>>>>
>>>>>    Thomas
>>>>
>>>>
>>>>
>>>
>
>
>