[Gmsh] Bounding Box of an imported STL Smaller than geometry?

[Baltasar Rüchardt]

Hi Christophe,

Wow, very nice, thank you! I do not notice anything being slow.

Thank you very much!

Baltasar

Am 24.06.20 um 13:16 schrieb Christophe Geuzaine:
> Hi Baltasar,
>
> Indeed we sub-sampled discrete entities to compute bounding boxes. I just changed this to a "brutal" bounding box computation in the latest dev snapshot: give it a try (If it's really too slow we should consider storing the information.)
>
> Christophe
>
>
>> On 23 Jun 2020, at 18:41, Baltasar Rüchardt <baltasar.ruechardt at ds.mpg.de> wrote:
>>
>> Dear everyone,
>>
>> I hope you are dealing as good as possible with the pandemic.
>>
>> I am puzzled because the bounding box that I obtain from a stl geometry
>> is smaller than the volume defined by the surface.
>>
>> The procedure used is as follows:
>>
>> 1. Import stl
>> 2. Use Bounding Box on surface
>> 3. Create Points by coordinates obtained from Bounding Box
>> 4. Connect points to make a volume.
>>
>> This is done in create_to_small_box.geo [which should have rather be
>> named create_too_small_box.geo ...].
>>
>> Background: The stl shows the surface of a heart obtained from a mrt
>> scan. I first shrink / expand it using the Plugin(Transform) and then I
>> want to translate it (again using the Plugin(Transform).Tz) such that
>> the tip of the heart is at the same height as the edge of an electrode
>> (small example in show_application_of_transforms.geo). My approach was
>> to use the bounding box zmin- value to compare the heights and then
>> calculate the necessary transformation by calculating tz= zmin_electrode
>> - zmin_heart .
>>
>> Does someone have a suggestion? Or any help? The alternative would be to
>> move the stl with meshlab such that the heart tip is at heigh zero, then
>> I could apply the shrinking and transform in gmsh without problems.
>>
>> Thank you very much in advance!
>>
>> Best regards
>>
>> Baltasar Rüchardt
>>
>>
>> Gmshinfo:
>>
>> Version       : 4.6.0
>> License       : GNU General Public License
>> Build OS      : MacOSX
>> Build date    : 20200622
>> Build host    : gmsh.info
>> Build options : 64Bit ALGLIB Ann Bamg Blas[custom] Blossom Cgns
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>> Lapack[custom] MathEx Med Mesh Metis Mmg3d Mpeg Netgen ONELAB
>> ONELABMetamodel OpenCASCADE OpenCASCADE-CAF OpenGL OptHom PETSc Parser
>> Plugins Png[fltk] Post QuadTri Solver TetGen/BR Voro++ Zlib[fltk]
>> FLTK version  : 1.4.0
>> PETSc version : 3.9.3 (real arithmtic)
>> OCC version   : 7.4.0
>> MED version   : 4.0.0
>> Packaged by   : geuzaine
>> Web site      : https://gmsh.info
>> Issue tracker : https://gitlab.onelab.info/gmsh/gmsh/issues
>> <bounding_box_smaller_than_stl.png><create_to_small_box.geo><outer_boundary.stl><show_application_of_transforms.geo>_______________________________________________
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> — 
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science 
> http://www.montefiore.ulg.ac.be/~geuzaine
>
>
>