[vtkusers] question about implicit surfaces and extractPolyDataGeometry - triangle mesh: getting elongated triangles

[Audette, Michel A.]

Hi again, 

I am able to get a cylinder, but I would like to produce a triangulated surface. However the triangles that I am getting, based on a wireframe visualization, are extremely elongated. I realize that this is probably something fairly obvious for VTK expert, but... Is there are VTK object that can postprocess my polygonal cylinder and produce a number of more compact triangles, suitable for a a finite-element study?

Cheers, 

Michel

Michel Audette, Ph.D.
Assistant Professor,
Department of Modeling, Simulation and Visualization Engineering,
Old Dominion University,
Norfolk, VA.
________________________________________
From: vtkusers-bounces at vtk.org [vtkusers-bounces at vtk.org] on behalf of Audette, Michel A. [maudette at odu.edu]
Sent: Thursday, July 18, 2013 3:25 PM
To: David Gobbi
Cc: vtkusers at vtk.org
Subject: [Spam:6.0 SpamScore] Re: [vtkusers] question about implicit surfaces and extractPolyDataGeometry - trying to produce a triangle mesh of a cylinder

Hi David,

thanks for your quick reply. I'll give it a try. I assume that a vtkTriangleFilter finishes the triangulation of the polydata.

Best wishes,

Michel

Michel Audette, Ph.D.
Assistant Professor,
Department of Modeling, Simulation and Visualization Engineering,
Old Dominion University,
Norfolk, VA.
________________________________________
From: David Gobbi [david.gobbi at gmail.com]
Sent: Thursday, July 18, 2013 3:18 PM
To: Audette, Michel A.
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] question about implicit surfaces and extractPolyDataGeometry - trying to produce a triangle mesh of a cylinder

Hi Michel,

The best way to produce a cylinder is usually to use vtkLineSource,
followed by vtkTubeFilter.  Use vtkLineSource::SetResolution to set
the resolution along the line, and vtkTubeFilter::SetNumberOfSides to
set the resolution around the cylinder.

Also, vtkTubeFilter::CappingOn() can be used to set whether the ends
of the cylinder are open or closed.

 - David

On Thu, Jul 18, 2013 at 12:52 PM, Audette, Michel A. <maudette at odu.edu> wrote:
> Dear VTK users,
>
> I would like to use a cylindrical implicit function in order to produce a
> triangulated cylindrical mesh. Looking at the testing example
> extractPolyData.tcl , which includes the code below, I see both a
> cylindrical function used as implicit function, as well as a sphere source
> which is used in conjunction with SetInputConnection. Can someone illuminate
> me on what purpose is served by the latter?
>
> If not, how can I produce a triangulated surface mesh of a cylinder, e.g.
> vtkCylinder?
>
> Here is the relevant code in the tcl test file.
>
> vtkSphereSource sphere
>   sphere SetThetaResolution 8
>   sphere SetPhiResolution 16
>   sphere SetRadius 1.5
>
> # Extraction stuff
> vtkTransform t
>     t RotateX 90
> vtkCylinder cylfunc
>     cylfunc SetRadius 0.5
>     cylfunc SetTransform t
> vtkExtractPolyDataGeometry extract
>     extract SetInputConnection [sphere GetOutputPort]
>     extract SetImplicitFunction cylfunc
>     extract ExtractBoundaryCellsOn
>
> vtkPolyDataMapper  sphereMapper
>     sphereMapper SetInputConnection [extract GetOutputPort]
>     sphereMapper GlobalImmediateModeRenderingOn
>
> vtkActor sphereActor
>     sphereActor SetMapper sphereMapper
>
> Thanks for your support.
>
> Michel
> Michel Audette, Ph.D.
> Assistant Professor,
> Department of Modeling, Simulation and Visualization Engineering,
> Old Dominion University,
> Norfolk, VA.


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