[Paraview] Rendering bug?

[Sven Buijssen]

Hi Ken,

Thanks for the elaborate explanation. I'll think of something.

Sven

----- Original Message -----
From: "Moreland, Kenneth" <kmorel at sandia.gov>
To: "Sven Buijssen" <sven.buijssen at tu-dortmund.de>, "paraview at paraview.org"
<paraview at paraview.org>
Sent: 11/11/09 15:48:59
Subject: [Paraview] Rendering bug?
> I do not think that this is a rendering problem.  I think you have just
> fooled the filter that extracts the external faces of the blocks (which
> is what is actually rendered).  Notice that when you arrange the
> overlapping meshes exactly as you are doing, that some of the faces are
> coincident.  In particular, the face that is missing is coincident.  Up
> to the point before you run clean to grid, these faces are topologically
> distinct because they use an independent (although coincident) set of
> points.  When you run clean to grid, these coincident points are merged.
>  When the points are merged, the cells from the two meshes now share the
> same indexed points.  At this point, these faces are no longer
> topologically distinct.  The external faces filter notices that these
> two faces use the same points and marks it as a neighbor face (this is
> the definition of a neighbor face) and “correctly” removes it.
> 
> The problem is basically that when you append the data sets you are
> creating a non-manifold mesh.  To correct the problem, you need some
> sort of filter that identifies coincident cells and removes duplicates.
>  I know of no such filter, so you will probably have to write your own.
> 
> -Ken
> 
> 
> On 11/11/09 7:33 AM, "Sven Buijssen" <sven.buijssen at tu-dortmund.de> wrote:
> 
>     Hi,
> 
>     I've come across something that I consider a rendering bug, but
>     before filing a
>     bug report I'd like to discuss it first. Maybe it sounds familiar.
>     (I'm guess
>     it's not related to the z-fighting issue discussed last week.)
> 
>     I have two volume grids consisting of hexaeder which partially
>     overlap (wavelet
>     sources for demonstration purposes in the attached *.pvsm file).
>     After applying
>     AppendDataSets and CleantoGrid filter it looks like the resulting
>     grid contains
>     all points and cells except the cell at the intersection of the two
>     grids. See
>     attached image.
>     But the "missing" cell is actually there. Twice. It can be confirmed
>     by applying
>     a ProgrammableFilter to add a cell array with cell numbers and
>     applying a
>     Threshold filter. Set both lower and upper threshold to either 0 or
>     30 to verify
>     that the "missing" cell is still there. It simply not rendered any more.
> 
>     It happens with PV 3.6.1 binary release and PV compiled from CVS
>     HEAD. (The
>     state file has been created with PV from CVS HEAD.)
> 
>     Any thoughts?
> 
>     Thanks
>     Sven
> 
> 
> 
>    ****      Kenneth Moreland
>     ***      Sandia National Laboratories
> ***********  
> *** *** ***  email: kmorel at sandia.gov
> **  ***  **  phone: (505) 844-8919
>     ***      web:   http://www.cs.unm.edu/~kmorel
>