[vtkusers] How to construct polygon?

Tue Apr 18 02:37:42 EDT 2017

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
>
> ___________________________________________
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/vtkusers/attachments/20170418/116d3f1b/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: non_planar_polygon.png
Type: image/png
Size: 92659 bytes
Desc: not available
URL: <http://public.kitware.com/pipermail/vtkusers/attachments/20170418/116d3f1b/attachment-0001.png>