[Gmsh] IDs of points forming a copy of entity (in python API)

[Christophe Geuzaine]

> On 15 Oct 2018, at 10:20, Marek Wojciechowski <mwojc at p.lodz.pl> wrote:
> 
> Hi!
> 
> I have a python script:
> 
> 
> 
> import gmsh
> import math
> 
> model = gmsh.model
> factory = model.occ
> 
> gmsh.initialize()
> gmsh.option.setNumber("General.Terminal", 1)
> 
> model.add("spline")
> 
> factory.addPoint(0.2,-1.6,0,0.1, 101) 
> factory.addPoint(1.2,-1.6,0,0.1, 102) 
> factory.addPoint(1.2,-1.1,0,0.1, 103) 
> factory.addPoint(0.3,-1.1,0,0.1, 104) 
> factory.addPoint(0.7,-1,0,0.1, 105) 
> 
> # periodic bspline through the control points
> factory.addSpline([103,102,101,104,105,103], 100)
> 
> # COPY SPLINE HERE
> dimTag = factory.copy([(1, 100)])
> 
> 
> 
> My question is how can i get a list of points forming copied spline?
> 

That's not possible, as the copy of the spline will actually only create a single point. The initial points used to construct the first spline are actually not used in its topological description: only their coordinates are needed internally by OpenCASCADE. If you look at the copy by adding e.g.

factory.synchronize()
gmsh.fltk.run()

at the end of your script, and if you select the new curve (101) in Tools->Visibility, you will see that it only depends on a single geometrical point (it is periodic). You can access that point with gmsh.model.getBoundary().

We could access, for each particular curve/surface type, the underlying parameters. In the case of a bspline like curve 101, we could access the poles, knots and multiplicities. Or for a circle, you could access the center. But there is no "general" way to access that data (unless we convert all curves to nurbs and give access to the parameters - which is probably not what you want).

Christophe


> 
> Regards,
> -- 
> Marek
> 
> 
> 
> 
> 
> --- 
> Politechnika Łódzka 
> Lodz University of Technology 
> 
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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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