[vtkusers] CT - VOLUME - CAD

[Ng Hong Wan]

I have access to FEM s/w Ansys and Abaqus, as well as CAD s/w like ProE
and Unigraphics installed in our university server.

I have written a parsing code in visual basic that is able to generate
outlines from vtkpolydatawriter format into ansys codes. But it is only
restricted to polylines, 

Moreover, I am dealing with volumes instead of surfaces and I am not
aware if any of the vtk classes available is able to generate triangular
volumes from CT scan, if yes, please advise me of the command.

FYI, there is a s/w called materialize mimics that claimed to be able to
do it, but I have not try it out. 

Thanks

-----Original Message-----
From: vtkusers-admin at public.kitware.com
[mailto:vtkusers-admin at public.kitware.com] On Behalf Of Budd Hirons
Sent: Wednesday, August 21, 2002 12:46 AM
To: vtk-users
Subject: Re: [vtkusers] CT - VOLUME - CAD

Hello,

 >> ... FEA meshing can be tricky business.

and how!

vtk does a great job of building polygonal surfaces from volume data and
we 
are trying to leverage that capabilities in our work, a significant part
of 
which is FEM/FEA using ABAQUS.

We are working on a method to import these vtk-generated surfaces 
(connected triangle patches such as BYU output) into PATRAN (a FEM 
pre-processing software package), which then creates a tetrahedral mesh 
from the imported surfaces. These meshes are being used as inputs into 
ABAQUS FEM code. While the method is looking promising, it is pretty
involved.

You may need to some sort of preprocessor such as PATRAN to do this.
Using 
CAD software as an intermediate step initially appears to be a nice 
shortcut, but for our FEM/FEA purposes introduces more complexity and 
licensing than it is worth.

Best,
Budd Hirons.


At 10:10 AM 8/20/2002 -0400, you wrote:

>Ng,
>
>In my limited experience so far, the file output options seem fairly 
>limited to
>triangle or other types of polygonal surfaces. If your CT data has nice

>borders
>in it, then you could use marching cubes to create the surface and then

>write an
>STL file (triangles) which most CAD packages can read, however in my 
>experience
>what the CAD folks are looking for are NURBS type surfaces which I've
not seen
>generated in vtk. Some CAD packages can drape NURBS surfaces on poly 
>meshes but
>I've not had much luck with that personally. I've not seen any meshing
>capabilities for FEA but I might be wrong here since I'm not real
familiar 
>with
>FEA. I'm fairly sure you can represent tets and hex volume meshes in
vtk 
>but how
>to do this from the CT data and whether these would be suitable for FEA

>I'm not
>sure. My coworkers tell me FEA meshing can be tricky business. It is
possible
>that I've missed some classes or that there are vtk user generated
classes out
>there that can handle these issues. Perhaps a search of the archives
might 
>turn
>something up.
>
>I hope folks can prove me wrong on a number of these statements as I'm
looking
>for some of these capabilities myself.......john
>
>
>
>From: "Ng Hong Wan" <hongwan at myrealbox.com>@public.kitware.com on
08/20/2002
>02:07 PM ZE8
> 
>
>       "Ng Hong Wan" 
> <hongwan at myrealbox.com>           To:   <vtkusers at public.kitware.com>
>                         @public.kitware.com           Cc:    (bcc:
John 
> Anast-JM/PGI)
>  Subject:      [vtkusers] CT - VOLUME - CAD
> 
>
>                                    Sent 
> by:
>           vtkusers-admin at public.kitware.com 
>
>                         08/20/2002 02:07 
> AM
>
>Hi,
>
>Is there a known approach to reconstruct a 3D volume model from CT
using 
>VTKand
>import it successfully into well known CAD modelers like Unigraphics,
Pro E,
>AutoCAD
>
>If not
>
>What abt a known approach toreconstruct a 3D volume model from CTusing
VTKand
>import it successfully into well knownFEA software like ABAQUS, ANSYS, 
>NASTRAN.

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