[Gmsh] Bug?

[sserebrinsky at gmail.com]

Hi Christophe,

I am Santiago Serebrinsky, perhaps you remember me from Caltech (I used 
to work with Michael Ortiz). I started using Gmsh, since I remembered 
that Laurent Stainier introduced me to it while we were office mates. I 
saw him juggling with his plots, so I gave it a chance. I like it very 
much, though I am still getting familiar with it. I write to you mainly 
about a possible bug, but I will take the opportunity to make some other 
comments too:

1- Is it possible that the triad changes from left to right handed upon 
drag-manipulation with the mouse? I had this impression several times, 
but I am not sure if it is simply a prejudice of mine while looking at 
what I called the left-handed image (see attachments), or if it can be 
mathematically proved that such image can actually only be interpreted 
as left-handed as I did.

2- It seemed to me that an extrusion extrudes not only the arguments of 
the Extrude command, but also all elementary entities in the bottom part 
of the bottom-up structure of the extruded entities. Is that right? Is 
it possible to detect/retrieve the ID number assigned to the extrusion 
of a particular elementary entity in the original extruded bottom-up 
structure?

3- Is it possible to generate a mesh symmetric about a given plane (by 
symmetry-copying another mesh)? I would like to do that, with a later 
recognition and removal of the nodes that lay at the symmetry plane by 
something like Coherence. If not (as I guess) do you plan to incorporate 
something like this? As of now, I am doing this manually (which is quite 
simple), but the upgrade would be very nice ;-)

4- Is it possible to refer in some way, in expressions, to all elements 
in a list (instead of enumerating all of them)? I found by trial and 
error that after
    extr[] = Extrude { 0, 0, B } { Surface{3,4}; } ;
I could use either
    symm[] = Symmetry { 0, 1, 0, 0 } { Duplicata{ Surface{ 3, 4, 
extr[0], extr[1], extr[2], extr[3], extr[4], extr[5], extr[6], extr[7], 
extr[8], extr[9], extr[10], extr[11], extr[12], extr[13], extr[14], 
extr[15], extr[16], extr[17], extr[18], extr[19], extr[20], extr[21], 
extr[22] }; } } ;
or
    symm[] = Symmetry { 0, 1, 0, 0 } { Duplicata{ Surface{ 3, 4, extr[] 
}; } } ;
which is much easier and versatile, but I wasn't sure if such usage is 
general, if Surface{ 3, 4, extr[] } is detecting which entities of 
extr[] are surfaces and neglecting the rest, etc. On the other hand, it 
seemed puzzling to me that, even if the previous command did the trick, 
a similar command but only for points
    symm[] = Symmetry { 0, 1, 0, 0 } { Duplicata{ Point{ extr[] }; } } ;
did not generate symmetric copies of all points in extr. Same happened 
with lines. Is there any way of performing these operations?

5- I would suggest that you add some examples after the enumeration of 
each command. They may be very helpful, beyond the tutorial, since they 
allow easy matching of the pattern with the example.

6-

Ok, good enough for now. Thanks for all, and please say hello to 
Laurent. Perhaps we meet at the WCCM8 (I will be there).

Best, from Argentina,

Santiago


PS: I apologize in advance if any of this was in the reference manual 
and I missed it.

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