[vtkusers] How to construct polygon?

rakesh patil prakeshofficial at gmail.com
Wed Apr 19 09:06:41 EDT 2017 

Hi Yoshimi,

I tried your sample code. It works for that set of input. Is it possible to
make it a generic algorithm? Like for any given set of inputs, will it work?

Thanks & Regards

On Tue, Apr 18, 2017 at 12:07 PM, rakesh patil <prakeshofficial at gmail.com>
wrote:

> Hi Andrew,
>
> I am trying to visualise a BRep object using VTK. I get the lines that
> forms a closed face. I create a vtkPolyData of each face and append it
> using vtkAppendPolyData. So the purpose is to visualise this BRep object as
> a wireframe as well as a surface. Seems that polygon rendering is not
> happening properly.
>
> I am able to connect those lines in sequence, to form a connected closed
> polygon. I face this problem only for the curved surface. For planar
> surfaces I don't see any issue. The data set shown in my sample code, is
> just one particular case. And for that case, Yoshimi's logic gives good
> surface representation. But I am not sure how far it will work for all the
> cases, I am in process to make it a generic one.
>
> Your inputs are welcome.
>
> Thanks & Regards
> Rakesh Patil
>
> On Tue, Apr 18, 2017 at 11:56 AM, Andrew Maclean <
> andrew.amaclean at gmail.com> wrote:
>
>> Hi Rakesh,
>>    I don't know what you intend to use it for. However if it is just a
>> one-off construction another suggestion would be to manually triangulate
>> the surface yourself.
>>
>> This is what is done for the VTK Parametric Functions.
>>
>> See void vtkParametricFunctionSource::MakeTriangles() and void
>> AddTriCells() in vtkParametricFunctionSource.cxx.
>>
>> Andrew
>>
>>
>>
>>> ---------- Forwarded message ----------
>>> From: rakesh patil <prakeshofficial at gmail.com>
>>> To: kenichiro yoshimi <rccm.kyoshimi at gmail.com>
>>> Cc: "vtkusers at vtk.org" <vtkusers at vtk.org>
>>> Bcc:
>>> Date: Mon, 17 Apr 2017 09:58:08 +0530
>>> Subject: Re: [vtkusers] How to construct polygon?
>>> Hi,
>>>
>>> I thought that vtkTriangleFilter does the tessellation of polygon by
>>> triangulating. Correct me if I am wrong. Let me try your suggestion and
>>> come back.
>>>
>>> Thanks
>>>
>>> On Mon, Apr 17, 2017 at 7:34 AM, kenichiro yoshimi <
>>> rccm.kyoshimi at gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> It looks like the issue of rendering concave polygons by OpenGL
>>>> included in the past mailing list, and it is concluded that OpenGL doesn't
>>>> render concave polygons properly and needs tessellation:
>>>> http://public.kitware.com/pipermail/vtkusers/2010-May/059784.html
>>>> http://vtk.1045678.n5.nabble.com/problems-rendering-concave-
>>>> polygon-td5007789.html
>>>> (I'm sorry I don't know the details of this problem.)
>>>>
>>>> I suggest using vtkDelaunay3D for tessellating and then using
>>>> vtkGeometryFilter that extracts the external faces.
>>>>
>>>> Thanks,
>>>> yoshimi
>>>>
>>>> 2017-04-17 3:30 GMT+09:00 rakesh patil <prakeshofficial at gmail.com>:
>>>>
>>>>> Hi,
>>>>>
>>>>> Well, I would like to know how polygon loop being non-planar leads to
>>>>> such output. Because, the image shown in expectedOutput is also built of
>>>>> similar polygon loop. Its just that for few curved surfaces are rendered
>>>>> properly and few don't. I just want to know why is there such inconsistent
>>>>> behavior and how do I overcome this?
>>>>>
>>>>> Thanks
>>>>>
>>>>> On Sat, Apr 15, 2017 at 10:56 AM, kenichiro yoshimi <
>>>>> rccm.kyoshimi at gmail.com> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Your polygon loop is non-planar.
>>>>>>
>>>>>> ​
>>>>>> Howerver, the triangulate method used by vtkPolygon assumes that
>>>>>> polygon points lie in a plane. I recommend to use vtkCylinderSource or
>>>>>> vtkStructuredGrid to represent the side of surface of a cylinder.
>>>>>>
>>>>>> Thanks,
>>>>>> yoshimi
>>>>>>
>>>>>> 2017-04-14 0:38 GMT+09:00 Rakesh Patil <rakesh.p at tataelxsi.co.in>:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>>
>>>>>>> This question seems to be simple, but I am not able to get any
>>>>>>> output for this. I am not able to understand what is happening in this case:
>>>>>>>
>>>>>>>
>>>>>>> vtkSmartPointer<vtkPoints> tpoints = vtkSmartPointer<vtkPoints>::New();
>>>>>>>
>>>>>>> vtkSmartPointer<vtkPolygon> poly = vtkSmartPointer<vtkPolygon>::New();
>>>>>>>
>>>>>>> vtkSmartPointer<vtkCellArray> carr = vtkSmartPointer<vtkCellArray>::New();
>>>>>>>
>>>>>>> vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 4.39116, -2.39117, 4.5));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 4.39116, -2.39117, 3));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 4.39116, -2.39117, 1.5));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 4.39116, -2.39117, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 4.08748, -2.87967, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 3.05391, -3.95899, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 1.74755, -4.68466, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( 0.28509, -4.99187, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -1.20284, -4.85316, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -2.58332, -4.28094, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -3.73305, -3.32631, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -4.54931, -2.07456, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -4.95919, -0.637487, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -4.92609, 0.856528, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -4.45295, 2.27403, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -3.58205, 3.4884, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -2.39117, 4.39116, 0));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -2.39117, 4.39116, 1.5));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -2.39117, 4.39116, 3));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -2.39117, 4.39116, 4.5));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -2.39117, 4.39116, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -3.58205, 3.4884, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -4.45295, 2.27403, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint( -4.92609, 0.856528, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(-4.95919, -0.637487, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(-4.54931, -2.07456, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(-3.73305, -3.32631, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(-2.58332, -4.28094, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(-1.20284, -4.85316, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(0.28509, -4.99187, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(1.74755, -4.68466, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(3.05391, -3.95899, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(4.08748, -2.87967, 6));
>>>>>>>
>>>>>>> poly->GetPointIds()->InsertNextId(tpoints->InsertNextPoint(4.39116, -2.39117, 6));
>>>>>>>
>>>>>>> carr->InsertNextCell(poly);
>>>>>>>
>>>>>>>
>>>>>>>     polyData->SetPoints(tpoints);
>>>>>>>
>>>>>>>     polyData->SetPolys(carr);
>>>>>>>
>>>>>>>
>>>>>>>     vtkSmartPointer<vtkTriangleFilter> tfilter = vtkSmartPointer<vtkTriangleFilter>::New();
>>>>>>>
>>>>>>>     tfilter->SetInputData(polyData);
>>>>>>>
>>>>>>>     tfilter->Update();
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>     vtkSmartPointer<vtkPolyDataMapper> pmapper = vtkSmartPointer<vtkPolyDataMapper>::New();
>>>>>>>
>>>>>>>     pmapper->SetInputConnection(tfilter->GetOutputPort());
>>>>>>>
>>>>>>>
>>>>>>>     vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
>>>>>>>
>>>>>>>     actor->SetMapper(pmapper);
>>>>>>>
>>>>>>>     actor->GetProperty()->SetRepresentationToSurface();
>>>>>>>
>>>>>>>     actor->GetProperty()->EdgeVisibilityOn();
>>>>>>>
>>>>>>>     actor->GetProperty()->SetEdgeColor(1.0, 0.0, 0.0);
>>>>>>>
>>>>>>>
>>>>>>>     renderer->AddActor(actor);
>>>>>>>
>>>>>>>     renderer->ResetCamera();
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> I am not able to view the output if I use vtkTriangleFilter. I have
>>>>>>> attached two screenshots. One is to show how the expected output should
>>>>>>> come. Another is the vtk's output without applying vtkTriangleFilter. How
>>>>>>> do I get the curved surfaces based on the above geometry (points)?
>>>>>>>
>>>>>>>
>>>>>>> Am I missing anything there?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Thanks & Regards
>>>>>>>
>>>>>>> Rakesh Patil
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> 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
>>>>>>>
>>>>>>> Search the list archives at: http://markmail.org/search/?q=vtkusers
>>>>>>>
>>>>>>> Follow this link to subscribe/unsubscribe:
>>>>>>> http://public.kitware.com/mailman/listinfo/vtkusers
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> 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
>>>>>>
>>>>>> Search the list archives at: http://markmail.org/search/?q=vtkusers
>>>>>>
>>>>>> Follow this link to subscribe/unsubscribe:
>>>>>> http://public.kitware.com/mailman/listinfo/vtkusers
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>>
>>>
>> --
>> ___________________________________________
>> Andrew J. P. Maclean
>>
>> ___________________________________________
>>
>
>
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