[Paraview] Displaying a flat polygon with multiple vertices

2011-07-13 Thread David Doria 
I have created a polygon with many vertices using vtkPolygon, then put it in
a vtkPolyData, and then saved it as a vtp file (attached). When I open it in
Paraview, it looks very broken (seems like backfaces are showing, things
are overlapping that shouldn't be, etc). If I run the TriangleFilter on it,
it looks fine. Is there something wrong with how I created the data? Or is
Paraview just not able to handle displaying something like this?

Thanks,

David


polygonClockwise.vtp
Description: Binary data
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Re: [Paraview] Displaying a flat polygon with multiple vertices

2011-07-13 Thread Burlen Loring 

Hi David,

I think that the issue is that the polygon you constructed is not 
convex. Figure 19-20 in VTK users guide is misleading because the 
example of VTK_POLYGON shows a non-convex polygon which as you found out 
doesn't work.


Burlen

On 07/13/2011 01:40 PM, David Doria wrote:
I have created a polygon with many vertices using vtkPolygon, then put 
it in a vtkPolyData, and then saved it as a vtp file (attached). When 
I open it in Paraview, it looks very broken (seems like backfaces 
are showing, things are overlapping that shouldn't be, etc). If I run 
the TriangleFilter on it, it looks fine. Is there something wrong with 
how I created the data? Or is Paraview just not able to handle 
displaying something like this?


Thanks,

David


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Re: [Paraview] Displaying a flat polygon with multiple vertices

2011-07-13 Thread Moreland, Kenneth 
I'd like to expand on Burlen's answer, which is correct.  VTK sort of handles 
concave polygons and sort of doesn't.  In particular, it does not render them 
correctly because the polygons are send directly to the OpenGL rendering 
system, which in turn does not handle them.  It would be possible for VTK to 
handle this correctly, but it would be inefficient in the common case where 
polygons are convex.

In general, filters should handle concave polygons correctly.  For example, run 
your polygon through the Triangulate filter.  It will be properly triangulated 
and will then render correctly.

This issue has shown up on the ParaView and VTK mailing lists before.  For a 
lengthy discussion, see this email thread:

http://markmail.org/message/e3fal43v6wzwkgm4

-Ken

     Kenneth Moreland
***  Sandia National Laboratories
***
*** *** ***  email: kmo...@sandia.gov
**  ***  **  phone: (505) 844-8919
***  web:   http://www.cs.unm.edu/~kmorel

From: Burlen Loring blor...@lbl.govmailto:blor...@lbl.gov
Date: Wed, 13 Jul 2011 14:01:55 -0700
To: David Doria daviddo...@gmail.commailto:daviddo...@gmail.com
Cc: ParaView paraview@paraview.orgmailto:paraview@paraview.org
Subject: Re: [Paraview] Displaying a flat polygon with multiple vertices

Hi David,

I think that the issue is that the polygon you constructed is not convex. 
Figure 19-20 in VTK users guide is misleading because the example of 
VTK_POLYGON shows a non-convex polygon which as you found out doesn't work.

Burlen

On 07/13/2011 01:40 PM, David Doria wrote:
I have created a polygon with many vertices using vtkPolygon, then put it in a 
vtkPolyData, and then saved it as a vtp file (attached). When I open it in 
Paraview, it looks very broken (seems like backfaces are showing, things are 
overlapping that shouldn't be, etc). If I run the TriangleFilter on it, it 
looks fine. Is there something wrong with how I created the data? Or is 
Paraview just not able to handle displaying something like this?

Thanks,

David


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