[Halla12_software] CAD format

[Zhiwen Zhao]

hi, Wouter

Thanks a lot for sharing.

On 12/07/2010 02:16 PM, Wouter Deconinck wrote:
> # Executive summary: GDML/persistency is useful, even if you don't
> export from CAD
>
> Hi all,
>
> For Qweak we investigated GDML as a possible option to get geometry
> data from CAD into Geant4.  I think there are two different aspects to
> the use of GDML/another persistency model, and it is best to keep them
> apart early on because they provide benefits independent of each
> other.
Those are very good insights.
>
> The first aspect is to have a meta-description of the geometry that
> can be modified without having to modify the Geant4 program code.
> This is generally referred to as 'persistency'.  This is equivalent to
> the role that euclid plays in geant3.  This is the role fulfilled by
> GDML, HDDS (Hall D geometry description), or LCDD, and could even be
> done completely in ROOT using the TGeo classes which interface nicely
> with TEve. You basically build up a database of geometrical objects
> which can be easily modified.  How you build up the database is not
> relevant in this aspect; I think Hall D edits those HDDS XML files by
> hand, but you could also use something fancier like the ROOT geometry
> editor and export to GDML.  The different XML-derived formats differ
> in how they treat active detectors and passive geometry elements.
> Implementing this for passive geometry elements is easy, but usually
> that's not very useful by itself (unless you only want to study
> collimator positions and shielding blocks).  The Qweak Geant4
> simulation has support for importing and exporting only passive GDML
> geometry elements.  Active elements are a lot/bit more difficult to
> implement, and they are not supported by the bare GDML standard so you
> need one of the extensions.
I think it's obvious that moller and solid will use some sort of XML.
LCDD extends GDML to have active elements.
>
> The second aspect is to be able to export the geometry that is stored
> in a CAD model into the persistency data format.  There are indeed
> programs available to transform STEP files into GDML (but they are not
> free).  In the CAD model you (likely) don't have a distinction between
> what is an 'active' detector and what is a 'passive' element, so that
> information is not present in the translation to GDML and has to be
> added by hand again.  This would require some thought on how to do
> this best (GDML can probably take string tags from comment fields in
> the STEP files).  Another limitation of the STEP->GDML programs that
> we have used is that they don't support exporting of tessellate
> objects.  Any non-standard element (e.g. the Qweak toroidal magnet
> 'spider' at the upstream end around the beam pipe) is not composed out
> of primitives but described as a tesselated volume.  This is lost in
> the translation that we used.
I think we can reply on converter to for passive elements only, and add 
active tag later.
No "support exporting of tessellate objects" is a common feature or just 
the tool you used? which one?
>
> There are various programs to go from CAD STEP files to GDML (prices
> are one year old and thus approximate).
> - There is Fastrad ($1k/year) which is intended for radiative dose
> simulations, mostly medical applications.  The free license for
> Fastrad allowed the export of up to 20 elements, although I think they
> bumped up the limit to a bit higher.  It is Windows only but runs in
> Wine.
> - ST-Tools ($23k+) is available, but we haven't tested it in Qweak (price).
> - And finally OpenFrontier, based on OpenCascade, developed by the
> European Space Agency for simulations of satellites, but that is only
> available to ESA member countries (Croatia, the only Qweak
> collaborator in Europe is not an ESA member).  In my opinion this
> looked like the best fit to what we (Qweak) needed, but was
> unfortunately unavailable to us, and not enough push by the
> collaboration to get something like this (and we started using
> Geant4/GDML too late anyway).  And unfortunately the website does not
> mention anything about OpenFrontier anymore, but it might have been
> included in ESABASE2.
Functionally is sometime more important than price, we may need to test 
them before making a purchase.
Don't we have moller members from Europe to get our hands on OpenFrontier?
>
> Cheers,
> Wouter
>
> http://esabase2.net/product/
> http://www.fastrad.net/ and http://www.trad.fr/
> https://caps.latech.edu/elog/R1+Software/090929_140014/stdev12prices2009.pdf
>
>
> On Tue, Dec 7, 2010 at 1:42 PM, Zhiwen Zhao<zwzhao at jlab.org>  wrote:
>> So the question would be how to convert some CAD format to GDML used by
>> ROOT and G4?
>>
>> by the way, I see SLAC has an extension to GDML
>> http://www.lcsim.org/software/lcdd/
>>
>> Zhiwen
>>
>> On 12/07/2010 12:12 PM, Krishna Kumar wrote:
>>> Hi, Zhiwen. We use SolidWorks, which is a good CAD program, but still
>>> not quite as good as what professional designers use. However,
>>> SolidWorks will put out several public formats that can be read into
>>> various other programs (so-called STEP files).
>>>
>>> Regarding SoLID, there is no plan to do CAD at moment. I dont think it
>>> is necessary. Since SoLID geometry is pretty standard, you can just
>>> start to build up the geometry in G4.
>>>
>>> cheers, KK
>>>
>>> On Dec 7, 2010, at 11:45 AM, Zhiwen Zhao wrote:
>>>
>>>> hi, KK
>>>>
>>>> I am thinking about the CAD conversion.
>>>> What CAD software you use for moller?
>>>> Can it output any sort-of-public format here
>>>> http://en.wikipedia.org/wiki/CAD_data_exchange
>>>>
>>>> Who does CAD for solid?
>>>>
>>>> Thanks
>>>>
>>>> Zhiwen
>>>>
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>
>
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