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Re: [LUG] 3d engineering

 

Hi,

If you want to get them into gmsh you could probably write your own
converter. The gmsh file format is pretty simple and for a lot of
problems i have written to it directly rather than using the GUI. The
problem here is due to the nature of what you are trying to do which
is FEA you need to define your problem in terms of surfaces and
volumes where as most mesh generation tools are purely verts and
surfaces. You could export 3d models as collada then process the
collada models to generate the required information for gmsh. But you
may need to get in to the hideous world of mesh deconvolution to
simplify meshes before injecting into FEA. Although with some care
when generating the model you could stop this being a problem.
Although there are nice decomp libs available, see
http://codesuppository.blogspot.co.uk/2011/05/hacd-hierarchical-approximate-convex.html
for that kind of work.

Collada provides a list of verts and triangles on a per object basis,
so you could convert those triangles in to surfaces and then map the
total volume per object. I just fear if you converted every GL tris
into a FEA surface it may get computationally expensive but its very
model specific anyway so YMMV and i may just be wrong about this as
boat hulls are very non linear shapes anyway so you probably do have
to have lots of surfaces to map accurately. But that is where decomp
will be very useful, run a high level of decomp initially to set
things up, then turn that down as you refine the model and want more
precision.

If you have not taken gmsh apart yet, all the file format is is a list
of indexed verts, a list of indexed lines that list two verts by id,
an indexed list of surfaces that list multiple lines by id (clockwise)
then holes anticlockwise, then a indexed list of volumes that
references surfaces.

Regards

Robin

On 22 October 2012 07:41, tom <tompotts@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> Currently I need to get models into gmsh and or Elmer. If I can get them
> into gmsh I think I can convert them for Elmer.
> As for what I want to achieve - anything! I've put my name down for a 64core
> 90Gflops
> http://www.kickstarter.com/projects/adapteva/parallella-a-supercomputer-for-everyone?ref=home_spotlight
> and in a couple of years its conceivable we will have teraflop processing.
> Main aim at the moment are stresses on boat hulls and near supersonic
> airflows in pulse/ram jets.
> Theres everything needed out there but it just doesnt join together that
> I've found....
> Tom te tom te tom
>
>
> On 21/10/12 21:40, Robin Cornelius wrote:
>>
>> What are you trying to achieve, what do you need to import the model into?
>>
>> Some possible convertors are meshlab, assimp viewer and autodesks fbx
>> convertor, but i fear these may all be mesh based formats and probably
>> not what you are after?
>>
>> On 21 October 2012 18:00, tom <tompotts@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>>>
>>> I'm trying to get some work done in Elmer or gmsh  but find the model
>>> building a bit slow and error prone.
>>> There's wings3d or blender which are a bit quicker at building models but
>>> cant convert to engineering grade formats.
>>> Has anyone experience of weapons grade work of this sort and can point me
>>> to
>>> some converters or something?
>>> Tom
>>>
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>
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