Thanks Christophe for clearing that up.
On Sun, Mar 31, 2019 at 10:49 AM Christophe Geuzaine <[email protected]> wrote: > > > > On 30 Mar 2019, at 21:32, Victor Kemp <[email protected]> wrote: > > > > Thanks Jeremy and Christophe. > > > > I think the manual might be wrong in saying that the default "" uses the > units from the file. I have a file with meters and inches but GMSH 4.2.2 > produces a mesh in millimeters. It also doesn't make sense to use the units > from the file because there can be more than one, and they're decided > arbitrarily by the software that created the file and not easily visible to > the user. Does the default value of Geometry.OCCTargetUnit really mean that > it uses OCCT's default, which is mm, and behaves the same as Gmsh 3? > > When "Geometry.OCCTargetUnit" is empty we don't specify any units, so > indeed we use OCCT's default behavior, so exactly as in Gmsh 3. I have > updated the documentation to clarify this. Thanks! > > > > > Also, is it unsafe to use "M" because of those bugs, or have they been > fixed? > > > > We've still experienced quite a few problems with "M" - which prompted the > change in the default value for the option in 4.2. > > Cheers, > > Christophe > > > > I mean 3.0.7, not 3.8. > > > > > > On Sun, Mar 31, 2019 at 2:21 AM Christophe Geuzaine <[email protected]> > wrote: > > > > > > > > > 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 > > > > > > > > > > _______________________________________________ > > > gmsh mailing list > > > [email protected] > > > http://onelab.info/mailman/listinfo/gmsh > > > > — > > Prof. Christophe Geuzaine > > University of Liege, Electrical Engineering and Computer Science > > http://www.montefiore.ulg.ac.be/~geuzaine > > > > > > > > — > Prof. Christophe Geuzaine > University of Liege, Electrical Engineering and Computer Science > http://www.montefiore.ulg.ac.be/~geuzaine > > > >
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