[Gmsh] meshing differences between version 1.65.0 and 2.0.4
David Colignon
David.Colignon at ulg.ac.be
Wed Mar 21 12:47:33 CET 2007
Daniel Wheeler wrote:
> Thanks for the prompt reply.
>
> On Mar 20, 2007, at 5:09 PM, David Colignon wrote:
>
>> Hi Daniel,
>>
>> yes, there are some differences in the default treatment of the
>> characteristic lengths ( lc ) between version 1.65 and 2.04.
>
>> In version 2 we added the ability to import iges or step files and in
>> this case there is no characteristic length associated to the points,
>> so we have to choose an arbitrary default value. The choice is
>> difficult because we have to be able to mesh very small as well as
>> very big objects, and also be able to merge step files (no lc) with
>> .geo files (imposed lc). And there is also the problem of imposed
>> background meshes and of attractor points.
>> We are still looking for he best compromise ...
>
> Fair enough.
>
>> We end up with a value for lc that can not be greater than 1/10 of the
>> largest dimension of the bounding box (to be able to mesh step files).
>
> I am trying to create a tapered mesh from a fine to a coarse region. If
> I want one edge to have only one or two elements then the
> rectangle must have a length that is 10 times greater than the width. Is
> that correct?
Yes, but I suppose it is not a good solution for you
You can also ad an isolated point
Point(999) = { 10 , 10 , 10 , spacing } ;
to artificially increase the size of the bounding box and get rid of this limitation.
>
>> If you want the same kind of behavior in version 2.04 as in version
>> 1.65, in _your_ case, you have to modify line 194 in
>> Mesh/BackgroundMesh.cpp :
>>
>> double l3 = CTX.lc / 10.;
>>
>> becomes
>>
>> double l3 = CTX.lc / 1.;
>>
>> and recompile.
>
> Not an option. The code is distributed to others. Could the divisor be
> made a parameter that is passed?
It could be... We are still looking for better solutions to this problem
Cheers,
Dave