[Gmsh] mesh from STEP file: correct units

[Victor Kemp]

I don't think it's right to say that the lengths should be in meters. STEP
files can have more than one length unit so it would be impossible to
satisfy all of them in the same mesh. Even when there's only one unit, if
Gmsh used that, you wouldn't know what it was without independently parsing
the STEP file, which nobody wants to do. So I think it's good that Gmsh
uses the same units all the time (mm) no matter what the STEP file says.
The units in STEP files seem to be pretty much useless - they're not the
same units that you used in the CAD model to specify dimensions either.

You can change the mm default with Geometry.OCCTargetUnit but I'm not sure
if it's available in 3.0.6. Someone else will be better able to help for
other ways to scale it.



On Wed, Apr 24, 2019 at 9:24 AM Marco Tiberga <M.Tiberga at tudelft.nl> wrote:

> Dear Gmsh developers,
>
>
>
> I want to create a mesh from a STEP file, loading it from a geo file.
>
> The mesh should be in m (as you can see from the step file, line 2916) ,
> but from the numbers I visualize in gmsh, I deduce the lengths are still
> expressed in mm (the entire domain should be around 2.5m high, but I see
> 2500).
>
>
>
> How can I perform the units conversion? I tried with
>
> *factor = 1.e-3;*
>
> *allpoints[] = Point "*";*
>
> *Dilate{{0,0,0},{factor,factor,factor}}{Point{allpoints[]};}*
>
> but it does not seem to work.
>
>
>
> I attached the .geo and the .stp files I am using. I use Gmsh 3.0.6.
>
>
>
> Thanks a lot for your help and sorry if the question is stupid, but I have
> little experience in using gmsh with step files.
>
>
>
> Best regards,
>
> Marco Tiberga
>
> PhD candidate
>
> Delft University of Technology
>
> Faculty of Applied Sciences
>
> Radiation Science & Technology Department
>
> Mekelweg 15, 2629 JB Delft, The Netherlands
>
> E-Mail: m.tiberga at tudelft.nl
>
> Website: http://www.nera.rst.tudelft.nl/
>
>
>
>
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