[Paraview] polygon rendered incorrectly

[Ken Martin]

Convex or concave?  If concave you need to triangle filter first. More
generally, if you have unknown polygons that could be convex, you need to
triangle filter first. Just guessing that is the issue.

Ken

On Sun, Feb 19, 2017 at 11:26 AM, Martin Rose <mrose81 at gmx.de> wrote:

> Greetings,
>
> I have generated a simple vtk file that contains a single polygon. The
> file is shown below.
>
> # vtk DataFile Version 2.0
> Output
> ASCII
> DATASET UNSTRUCTURED_GRID
> POINTS 6 float
> 0.0048265 0.00753943 0
> 0.0048265 0.00752686 0
> 0.00485421 0.00752571 0
> 0.00485266 0.00750789 0
> 0.00485804 0.00750789 0
> 0.00485804 0.00753943 0
> CELLS 1 7
> 6 0 1 2 3 4 5
> CELL_TYPES 1
> 7
> #end of file
>
>
> After loading the file in paraview, the surface of the polygon is not
> displayed correctly. It seems that an additional triangle is displayed.
> However, the wireframe is displayed correctly. I have checked the order of
> points and confirmed that the order is correct. I also multiplied the
> coordinates by 100 but the problem persists.
>
> If I add the first  point of the polygon again, the surface is displayed
> correctly. The modified lines read:
> CELLS 1 8
> 7 0 1 2 3 4 5 0
>
> Unfortunately, that fix does not work for other polygons that show the
> same problem.
> Is there something wrong with my vtk file?
>
> Greetings,
> Martin
>
>
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-- 
Ken Martin PhD
Chairman & CFO
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065
518 371 3971

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