[Gmsh] strange behavior of layer extrusion

[Christophe Geuzaine]

> On 19 Dec 2019, at 21:24, Marco Antolovic <marco_antolovic at yahoo.it> wrote:
> 
> Hi all,
> 
> I have noticed a strange behavior for layered extrusion. It appears that if you first extrude a point to line and then operate a translation on the line than the layering is lost:
> 

That's currently (unfortunately) normal. Extruded meshes rely on the fact that the mesher knows how the geometry was constructed: currently as soon as a geometrical entity is modified, we assume that this relationship is lost.

We should handle translations and other simple transforms and modify the extrusion functions accordingly - but that's in the TODO list. Don't hesitate to contribute a patch if this is critical for your workflow.

Christophe



> my GMSH version is version 4.5.0-git-a2a0ecd on a Mac
> 
> below is my code:
> 
> SetFactory("OpenCASCADE");
> 
> trace_width = DefineNumber[ 1, Min .01, Max 1000, Step .01, Name "  Track parameters/trace width (mm)"  ];
> trace_width = trace_width/1000;
> 
> trace_thickness = DefineNumber[ 1, Min .01, Max 1000, Step .01, Name "  Track parameters/trace thickness (mm)"  ];
> trace_thickness = trace_thickness/1000;
> 
> trace_start_right = newp;
> Point(trace_start_right) = {0, 0, -trace_thickness/2, trace_width};
> extrude_point = Extrude {-trace_width, 0, 0}{ Point{trace_start_right}; Layers { 3 };};
> trace_width_line = extrude_point(1);
> Translate { -.1, .1, 0 } { Line{trace_width_line}; } // this operation voids the Layers{3} request
> 
> Is this normal?
> 
> Many thanks,
> 
> Marco
> 
> 
>  
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine