> On 30 Mar 2019, at 08:22, Victor Kemp <[email protected]> wrote:
>
> How does Gmsh decide what units to use for its dimensionless mesh made from a
> STEP file? I've noticed that different versions seem to do it differently. Is
> there a setting to control this or likely future stability? It seems to
> change unpredictably with each new version and that makes interoperability
> with other software difficult.
>
> Version 3.early: millimeter
> Version 3.8: meter
Gmsh 2 and 3 used the coordinates in STEP files as-is, i.e. didn't handle units
at all. (Note that Gmsh 3.8 does not exist.)
> Version 4.0: meter
> Version 4.1: meter
Gmsh 4 introduced a mechanism to choose the unit, through the
"Geometry.OCCTargetUnit" option, as mentioned by Jeremy.
The default value for that option was "M" (meters) in Gmsh 4.0 and Gmsh 4.1.
This however led to several regressions, as the conversion for files written in
other units (millimeters, inches, etc.) would sometimes lead to subtle
artefacts in the geometry.
> Version 4.2: millimeter
>
So in Gmsh 4.2, the default value of "Geometry.OCCTargetUnit" has been set to
"" (i.e. empty). This means that we don't translate units by default; but you
can set the option to your preferred unit if you want to.
Christophe
>
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—
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine
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