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Hello,<BR>
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As suggested by some, I tried vtkTriangleFilter to tessellate concave polygons. It almost works, except some bright pixels appearing within the polygon forming streak like lines as well as some at the boundary. Attached is a typical example of such a streak. This streaks appear or disappear as the magnification changes. I think they come from overlapped pixels from neighouring triangles. I need suggestions in how to remove them.<BR>
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Thanks!<BR><BR>Xiaofeng<BR><BR><BR> <BR>> From: dave.demarle@kitware.com<BR>> Date: Thu, 6 May 2010 11:15:23 -0400<BR>> Subject: Re: [vtkusers] Bug or Design: Rendering concave polygons with vtkActor2D<BR>> To: xf10036@hotmail.com<BR>> CC: vtkusers@vtk.org<BR>> <BR>> Try vtkTriangleFilter.<BR>> <BR>> If there is a better alternative hopefully someone on list with more<BR>> mesh experience than I will fill in the details.<BR>> <BR>> David E DeMarle<BR>> Kitware, Inc.<BR>> R&D Engineer<BR>> 28 Corporate Drive<BR>> Clifton Park, NY 12065-8662<BR>> Phone: 518-371-3971 x109<BR>> <BR>> <BR>> <BR>> On Thu, May 6, 2010 at 11:06 AM, Xiaofeng Z <xf10036@hotmail.com> wrote:<BR>> > David,<BR>> ><BR>> > I am thinking of using GLU to perform Tessellation. I wonder how involved<BR>> > it would be if I try to do it inside VTK.<BR>> ><BR>> > I would appreciate it if you can provide some insight.<BR>> ><BR>> > Thanks!<BR>> ><BR>> > Xiaofeng<BR>> ><BR>> ><BR>> ><BR>> ><BR>> >> From: dave.demarle@kitware.com<BR>> >> Date: Wed, 5 May 2010 07:51:40 -0400<BR>> >> Subject: Re: [vtkusers] Bug or Design: Rendering concave polygons with<BR>> >> vtkActor2D<BR>> >> To: xf10036@hotmail.com<BR>> >> CC: vtkusers@vtk.org<BR>> >><BR>> >> I suspect that is because OpenGL doesn't render concave polygons<BR>> >> properly, thus VTK, which uses GL to render, doesn't either. So<BR>> >> unfortunately you have to tesselate that into a set convex polygons in<BR>> >> order to have it drawn properly.<BR>> >><BR>> >> David E DeMarle<BR>> >> Kitware, Inc.<BR>> >> R&D Engineer<BR>> >> 28 Corporate Drive<BR>> >> Clifton Park, NY 12065-8662<BR>> >> Phone: 518-371-3971 x109<BR>> >><BR>> >><BR>> >><BR>> >> On Tue, May 4, 2010 at 11:38 AM, Xiaofeng Z <xf10036@hotmail.com> wrote:<BR>> >> > Concave polygons are not rendered as expected with vtkPolyDataMapper and<BR>> >> > vtkActor2D (see below). Is it by design or is it a bug? If it's by<BR>> >> > design,<BR>> >> > is there any flag can be set to alter the rendering behaviour?<BR>> >> ><BR>> >> > Thanks!<BR>> >> ><BR>> >> > Xiaofeng<BR>> >> ><BR>> >> > Hi all,<BR>> >> ><BR>> >> > How do I make uniform transparency in a concave polygon, instead of<BR>> >> > getting<BR>> >> > multiple shades, e.g. in the attached graph?<BR>> >> ><BR>> >> > The polygon are created with:<BR>> >> ><BR>> >> > vtkPoints* points = vtkPoints::New();<BR>> >> > vtkCellArray* cells = vtkCellArray::New();<BR>> >> > points->SetNumberOfPoints(4);<BR>> >> ><BR>> >> > // create a concave polygon (equilateral with a cutout at the bottom)<BR>> >> ><BR>> >> > points->SetPoint(0, 10.0, 10.0, 0.0);<BR>> >> > points->SetPoint(1, 110.0, 183.2, 0.0);<BR>> >> > points->SetPoint(2, 210.0, 10.0, 0.0);<BR>> >> > points->SetPoint(3, 110.0, 110.0, 0.0);<BR>> >> > cells->Allocate(1, 5);<BR>> >> > cells->InsertNextCell(5);<BR>> >> > cells->InsertCellPoint(0);<BR>> >> > cells->InsertCellPoint(1);<BR>> >> > cells->InsertCellPoint(2);<BR>> >> > cells->InsertCellPoint(3);<BR>> >> > cells->InsertCellPoint(0);<BR>> >> > vtkPolyData* poly = vtkPolyData::New();<BR>> >> > poly->Initialize();<BR>> >> > poly->SetGlobalWarningDisplay(1);<BR>> >> > poly->SetPoints(points);<BR>> >> > poly->SetPolys(cells);<BR>> >> ><BR>> >> > A vtkActor2D and a vtkPolyDataMapper2D was used for the rendering.<BR>> >> ><BR>> >> > Many thanks!<BR>> >> > Xiaofeng<BR>> >> ><BR>> >> ><BR>> >> ><BR>> >> > ________________________________<BR>> >> > The New Busy think 9 to 5 is a cute idea. Combine multiple calendars<BR>> >> > with<BR>> >> > Hotmail. Get busy.<BR>> >> > ________________________________<BR>> >> > Hotmail has tools for the New Busy. Search, chat and e-mail from your<BR>> >> > inbox.<BR>> >> > Learn more.<BR>> >> > _______________________________________________<BR>> >> > Powered by www.kitware.com<BR>> >> ><BR>> >> > Visit other Kitware open-source projects at<BR>> >> > http://www.kitware.com/opensource/opensource.html<BR>> >> ><BR>> >> > Please keep messages on-topic and check the VTK FAQ at:<BR>> >> > http://www.vtk.org/Wiki/VTK_FAQ<BR>> >> ><BR>> >> > Follow this link to subscribe/unsubscribe:<BR>> >> > http://www.vtk.org/mailman/listinfo/vtkusers<BR>> >> ><BR>> >> ><BR>> ><BR>> > ________________________________<BR>> > The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with<BR>> > Hotmail. Get busy.<BR> <br /><hr />Hotmail has tools for the New Busy. Search, chat and e-mail from your inbox. <a href='http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_1' target='_new'>Learn more.</a></body>
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