[vtkusers] Bug in vtkStripper on a very simple case ?
Goodwin Lawlor
goodwin.lawlor.lists at gmail.com
Thu Dec 20 11:05:32 EST 2012
JD,
Pass the final polyline through vtkCleanPolyData with 0.0 tolerance (the
default) and it should remove the coincident points.
hth
Goodwin
On Thu, Dec 20, 2012 at 12:42 AM, pof <jd379252 at gmail.com> wrote:
> Goodwin,
>
> I tested the patch on the following simple case (5 segments)
> # vtk DataFile Version 3.0
> vtk output
> ASCII
> DATASET POLYDATA
> POINTS 6 float
> 1.7 0.5 0 2 0 0 1.7 -0.5 0
> 1.6 -1 0 1.8 -0.2 0 1.6 1 0
> LINES 5 15
> 2 0 1
> 2 2 3
> 2 4 2
> 2 1 4
> 2 5 0
>
> without the patch, 2 polylines are obtained from the vtkStripper
> LINES 2 9
> 5 0 1 4 2 3
> 2 5 0
>
> whereas with the patch a single polyline is obained
> LINES 1 8
> 7 5 0 0 1 4 2 3
>
> Things are of course better, though a duplicate of one point (point 0 in
> this case) is obtained, which should obviously have been avoided.
> So it looks there's stil some space to improve the patch.
>
> In any case, I thank you for sharing this information with me.
> JD
>
>
> Le 19/12/2012 10:04, Goodwin Lawlor a écrit :
>
> I think vtkStripper was originally written to quickly produce
> vtkTriangleStrip/vtkPolyLine primitives that would render faster, not a
> computational geometry type class that would produce the longest possible
> polylines... it is a visualization library after all.
>
> The seed point is arbitrary so you may not get the outcome you were
> looking for.
>
> See this 2002 post, that contains a patch which may help:
> http://vtk.org/pipermail/vtkusers/2002-January/009372.html
>
> There was a bug report too:
> http://www.vtk.org/Bug/print_bug_page.php?bug_id=832
>
> hth
>
> Goodwin
>
>
> On Mon, Dec 10, 2012 at 2:51 AM, David Gobbi <david.gobbi at gmail.com>wrote:
>
>> Insert vtkTriangleFilter before vtkStripper. This will break any
>> input polylines into line segments. I don't know if it will help,
>> but it might.
>>
>> - David
>>
>> On Sun, Dec 9, 2012 at 2:48 PM, pof <jd379252 at gmail.com> wrote:
>> > yes this is the way LINES objects are written on vtk files.
>> > Ok, so I understand now the point you were making about the "T", which
>> was
>> > uncorrect.
>> >
>> > So back to the problem, why this vtkStripper is not able to merge those
>> 2
>> > lines?
>> >
>> > Le 09/12/2012 21:41, David Gobbi a écrit :
>> >>
>> >> Is it? Maybe it is. When you wrote the numbers, I assumed that
>> >>
>> >> all of the numbers that you listed were just point indices.
>> >>
>> >>
>> >> On Sun, Dec 9, 2012 at 1:37 PM, pof <jd379252 at gmail.com> wrote:
>> >>>
>> >>> Hum I see.
>> >>> (from what I understand), the first integer of each line is simply the
>> >>> number of points of the corresponding LINE
>> >>>
>> >>> Le 09/12/2012 21:33, David Gobbi a écrit :
>> >>>
>> >>>> Then where would the "9" go?
>> >>>>
>> >>>> The stripper uses a simple algorithm, it just chooses a starting
>> >>>> point, goes as far as it can in each direction to create the first
>> >>>> polyline, and then repeats this procedure until all the line segments
>> >>>> are accounted for. It doesn't exhaustively search though all
>> >>>> permutations to see which one gives the smallest number of output
>> >>>> polylines... that would cause the algorithm to run many times slower.
>> >>>>
>> >>>>
>> >>>>
>> >>>>
>> >>>> On Sun, Dec 9, 2012 at 1:12 PM, pof <jd379252 at gmail.com> wrote:
>> >>>>>
>> >>>>> Hi David
>> >>>>>
>> >>>>> the first polyline being:
>> >>>>>
>> >>>>> 9 0 1 2 3 4 5 19 6 7
>> >>>>> and the third polyline (actually it is a segment) being:
>> >>>>> 2 18 0
>> >>>>> I don't see why they shoud not merge together as (unless I
>> >>>>> misunderstand
>> >>>>> something):
>> >>>>> 10 18 0 1 2 3 4 5 19 6 7
>> >>>>>
>> >>>>> Am I wrong?
>> >>>>>
>> >>>>>
>> >>>>> Le 09/12/2012 21:05, David Gobbi a écrit :
>> >>>>>
>> >>>>>> Hi JD,
>> >>>>>>
>> >>>>>> It could only merge those two lines if it joined them with a "T".
>> >>>>>> A polyline cannot have any branches.
>> >>>>>>
>> >>>>>> - David
>> >>>>>>
>> >>>>>>
>> >>>>>> On Sun, Dec 9, 2012 at 12:16 PM, pof <jd379252 at gmail.com> wrote:
>> >>>>>>>
>> >>>>>>> Hi all,
>> >>>>>>>
>> >>>>>>> I get a strange result (which may be a bug) using vtk stripper,
>> i.e.
>> >>>>>>> it
>> >>>>>>> does
>> >>>>>>> not merge LINES as polylines as it is expected to.
>> >>>>>>> In this example (see below an extract of the polydata produced by
>> >>>>>>> vtkStripper), only 2 polylines should be obtained, but vtkStripper
>> >>>>>>> forgot
>> >>>>>>> to
>> >>>>>>> merge the first and the third line together, though they obviously
>> >>>>>>> share
>> >>>>>>> point with Id=0 (btw, the fact that only Id 0 remains unmerged
>> might
>> >>>>>>> not
>> >>>>>>> be
>> >>>>>>> pure luck).
>> >>>>>>>
>> >>>>>>> LINES 3 24
>> >>>>>>> 9 0 1 2 3 4 5 19 6 7
>> >>>>>>> 10 9 8 17 13 12 15 14 11 10 16
>> >>>>>>> 2 18 0
>> >>>>>>> Does anybody have an idea or an explanation?
>> >>>>>>> Thanks
>> >>>>>>> JD
>> >>>>>>>
>> >>>>>>> PS: Here below is the complete source file that generates these
>> data
>> >>>>>>> and
>> >>>>>>> in
>> >>>>>>> which vtkStripper is used.
>> >>>>>>>
>> >>>>>>> //////////////////////////////////////////////////////
>> >>>>>>> // Example modified from IntersectionPolyDataFilter.cxx
>> >>>>>>> //////////////////////////////////////////////////////
>> >>>>>>> #include <vtkActor.h>
>> >>>>>>> #include <vtkIntersectionPolyDataFilter.h>
>> >>>>>>> #include <vtkPolyDataMapper.h>
>> >>>>>>> #include <vtkPolyDataWriter.h>
>> >>>>>>> #include <vtkProperty.h>
>> >>>>>>> #include <vtkRenderer.h>
>> >>>>>>> #include <vtkRenderWindow.h>
>> >>>>>>> #include <vtkRenderWindowInteractor.h>
>> >>>>>>> #include <vtkSmartPointer.h>
>> >>>>>>> #include <vtkSphereSource.h>
>> >>>>>>> #include <vtkCellArray.h>
>> >>>>>>> #include <vtkStripper.h>
>> >>>>>>>
>> >>>>>>> int main(int argc, char *argv[])
>> >>>>>>> {
>> >>>>>>> vtkSmartPointer<vtkSphereSource> sphereSource1 =
>> >>>>>>> vtkSmartPointer<vtkSphereSource>::New();
>> >>>>>>> sphereSource1->SetCenter(0.0, 0.0, 0.0);
>> >>>>>>> sphereSource1->SetRadius(2.0f);
>> >>>>>>> sphereSource1->SetPhiResolution(20);
>> >>>>>>> sphereSource1->SetThetaResolution(20);
>> >>>>>>> sphereSource1->Update();
>> >>>>>>> vtkSmartPointer<vtkPolyDataMapper> sphere1Mapper =
>> >>>>>>> vtkSmartPointer<vtkPolyDataMapper>::New();
>> >>>>>>> sphere1Mapper->SetInputConnection(
>> >>>>>>> sphereSource1->GetOutputPort()
>> >>>>>>> );
>> >>>>>>> sphere1Mapper->ScalarVisibilityOff();
>> >>>>>>> vtkSmartPointer<vtkActor> sphere1Actor =
>> >>>>>>> vtkSmartPointer<vtkActor>::New();
>> >>>>>>> sphere1Actor->SetMapper( sphere1Mapper );
>> >>>>>>> sphere1Actor->GetProperty()->SetOpacity(.3);
>> >>>>>>> sphere1Actor->GetProperty()->SetColor(1,0,0);
>> >>>>>>>
>> >>>>>>> /////////////////////////
>> >>>>>>> // BEGIN MODIFICATIONS //
>> >>>>>>> /////////////////////////
>> >>>>>>> // Create a planar object
>> >>>>>>> // Define 4 vertices
>> >>>>>>> vtkSmartPointer<vtkPoints> PlanePoints =
>> >>>>>>> vtkSmartPointer<vtkPoints>::New();
>> >>>>>>> vtkSmartPointer<vtkCellArray> PlaneCells =
>> >>>>>>> vtkSmartPointer<vtkCellArray>::New();
>> >>>>>>> PlanePoints->InsertNextPoint(-3, -1, 0);
>> >>>>>>> PlanePoints->InsertNextPoint(3, -1, 0);
>> >>>>>>> PlanePoints->InsertNextPoint(-3, 1, 0);
>> >>>>>>> PlanePoints->InsertNextPoint(3, 1, 0);
>> >>>>>>> // Create 2 trianglar faces
>> >>>>>>> PlaneCells->InsertNextCell(3);
>> >>>>>>> PlaneCells->InsertCellPoint(0);
>> >>>>>>> PlaneCells->InsertCellPoint(1);
>> >>>>>>> PlaneCells->InsertCellPoint(2);
>> >>>>>>> PlaneCells->InsertNextCell(3);
>> >>>>>>> PlaneCells->InsertCellPoint(1);
>> >>>>>>> PlaneCells->InsertCellPoint(3);
>> >>>>>>> PlaneCells->InsertCellPoint(2);
>> >>>>>>> // Create the polydata from points and faces
>> >>>>>>> vtkSmartPointer<vtkPolyData> ProtectionWall =
>> >>>>>>> vtkSmartPointer<vtkPolyData>::New();
>> >>>>>>> ProtectionWall->SetPoints(PlanePoints);
>> >>>>>>> ProtectionWall->SetPolys(PlaneCells);
>> >>>>>>> /////////////////////////
>> >>>>>>> // END MODIFICATIONS //
>> >>>>>>> /////////////////////////
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkPolyDataMapper> planeMapper =
>> >>>>>>> vtkSmartPointer<vtkPolyDataMapper>::New();
>> >>>>>>> planeMapper->SetInputConnection(
>> >>>>>>> ProtectionWall->GetProducerPort()
>> >>>>>>> );
>> >>>>>>> planeMapper->ScalarVisibilityOff();
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkActor> planeActor =
>> >>>>>>> vtkSmartPointer<vtkActor>::New();
>> >>>>>>> planeActor->SetMapper( planeMapper );
>> >>>>>>> planeActor->GetProperty()->SetOpacity(.3);
>> >>>>>>> planeActor->GetProperty()->SetColor(0,1,0);
>> >>>>>>>
>> >>>>>>> // Get intersection segments (LINES) using the
>> >>>>>>> vtkIntersectionPolyDataFilter
>> >>>>>>> vtkSmartPointer<vtkIntersectionPolyDataFilter>
>> >>>>>>> intersectionPolyDataFilter
>> >>>>>>> = vtkSmartPointer<vtkIntersectionPolyDataFilter>::New();
>> >>>>>>> intersectionPolyDataFilter->SplitFirstOutputOff();
>> >>>>>>> intersectionPolyDataFilter->SplitSecondOutputOff();
>> >>>>>>> intersectionPolyDataFilter->SetInputConnection( 0,
>> >>>>>>> sphereSource1->GetOutputPort() );
>> >>>>>>> intersectionPolyDataFilter->SetInputConnection( 1,
>> >>>>>>> ProtectionWall->GetProducerPort() );
>> >>>>>>> intersectionPolyDataFilter->Update();
>> >>>>>>>
>> >>>>>>> /////////////////////////
>> >>>>>>> // BEGIN MODIFICATIONS //
>> >>>>>>> /////////////////////////
>> >>>>>>> // Try to get the polylines (there should be 2) from the
>> >>>>>>> segments
>> >>>>>>> (LINES)
>> >>>>>>> vtkSmartPointer<vtkStripper> stripper =
>> >>>>>>> vtkSmartPointer<vtkStripper>::New();
>> >>>>>>>
>> >>>>>>>
>> >>>>>>>
>> >>>>>>>
>> stripper->SetInputConnection(intersectionPolyDataFilter->GetOutputPort());
>> >>>>>>> stripper->Update();
>> >>>>>>> // Save resulting polydata on a file, in which we see that
>> there
>> >>>>>>> are 3
>> >>>>>>> polylines (actually the second polyline is ok,
>> >>>>>>> // but the first and third polylines should have been further
>> >>>>>>> merged
>> >>>>>>> vtkSmartPointer<vtkPolyDataWriter> wr =
>> >>>>>>> vtkSmartPointer<vtkPolyDataWriter>::New();
>> >>>>>>> wr->SetFileName("polylines.txt");
>> >>>>>>> wr->SetInputConnection(stripper->GetOutputPort());
>> >>>>>>> wr->Write();
>> >>>>>>> ///////////////////////
>> >>>>>>> // END MODIFICATIONS //
>> >>>>>>> ///////////////////////
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkPolyDataMapper> intersectionMapper =
>> >>>>>>> vtkSmartPointer<vtkPolyDataMapper>::New();
>> >>>>>>> intersectionMapper->SetInputConnection(
>> >>>>>>> stripper->GetOutputPort()
>> >>>>>>> );
>> >>>>>>> intersectionMapper->ScalarVisibilityOff();
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkActor> intersectionActor =
>> >>>>>>> vtkSmartPointer<vtkActor>::New();
>> >>>>>>> intersectionActor->SetMapper( intersectionMapper );
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkRenderer> renderer =
>> >>>>>>> vtkSmartPointer<vtkRenderer>::New();
>> >>>>>>> renderer->AddViewProp(sphere1Actor);
>> >>>>>>> renderer->AddViewProp(planeActor);
>> >>>>>>> renderer->AddViewProp(intersectionActor);
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkRenderWindow> renderWindow =
>> >>>>>>> vtkSmartPointer<vtkRenderWindow>::New();
>> >>>>>>> renderWindow->AddRenderer( renderer );
>> >>>>>>>
>> >>>>>>> vtkSmartPointer<vtkRenderWindowInteractor> renWinInteractor =
>> >>>>>>> vtkSmartPointer<vtkRenderWindowInteractor>::New();
>> >>>>>>> renWinInteractor->SetRenderWindow( renderWindow );
>> >>>>>>>
>> >>>>>>> renderWindow->Render();
>> >>>>>>> renderWindow->SetSize(600, 600);
>> >>>>>>> renderer->SetBackground(0.1, 0.2, 0.4);
>> >>>>>>> renWinInteractor->Start();
>> >>>>>>>
>> >>>>>>> return EXIT_SUCCESS;
>> >>>>>>> }
>> >>>>>
>> >>>>>
>> >
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
>> http://www.kitware.com/opensource/opensource.html
>>
>> Please keep messages on-topic and check the VTK FAQ at:
>> http://www.vtk.org/Wiki/VTK_FAQ
>>
>> Follow this link to subscribe/unsubscribe:
>> http://www.vtk.org/mailman/listinfo/vtkusers
>>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20121220/ae7074fa/attachment.htm>
More information about the vtkusers
mailing list