Dear all,
I figured it out (I know, I really should try harder before posting...).
Here is a snippet to constrain the y component of some vertices:
dofs = mfu.basic_dof_nodes();
# Count the total number of constrains.
num_constraints = 0;
for i in range(0, mfu.nbdof()):
if (abs(dofs[1][i] + 0.00125) < 1e-9): # A condition to
determine which vertex to constrain
if (i % 3 != 1): continue; # If not y component, move on to
next dof
num_constraints = num_constraints + 1;
H = gf.Spmat('empty', num_constraints, mfu.nbdof());
# Fill H and R
row_index = 0;
for i in range(0, mfu.nbdof()):
if (abs(dofs[1][i] + 0.00125) < 1e-9):
if (i % 3 != 1): continue;
H.assign(row_index, i, 1);
row_index = row_index + 1;
R.append(0);
b4 = gf.MdBrick("constraint", b2, 'eliminated');
b4.constraints(H, R);
Hope it is helpful to someone else too.
James
On Fri, Oct 28, 2011 at 12:18 PM, James Zhou <[email protected]> wrote:
> Hi Yves,
>
> Could you elaborate on how to use the old constraint block a little bit? I
> keep getting dimension mismatch errors. When qdim is not 1, is the
> constraint matrix is of size nb_constraints x (nb_dof * qdim)?
>
> In the new brick system, is it possible to add pointwise constraint with
> elimination?
>
> Thank you very much :)
> James
>
>
> On Fri, Oct 28, 2011 at 4:26 AM, Yves Renard <[email protected]>wrote:
>
>>
>> Dear James,
>>
>> The (old) brick on which you refer take a global constraint matrix in
>> argument. This should be a global matrix (nb_constraints x nb_dof)
>>
>> Note that in the new brick system, there is now a special brick to set
>> components on specific points (for instance to kill rigid body modes). The
>> points are not necessarily some vertices of the mesh. This is the
>> "pointwise
>> constraints brick". It is available in the svn version only.
>>
>> Yves.
>>
>>
>>
>> On vendredi 28 octobre 2011, James Zhou wrote:
>> > Dear all,
>> >
>> > I have exactly the same question as in
>> > http://www.mail-archive.com/[email protected]/msg00142.html
>> >
>> > In particular, I want to fixed a component of some a set of vertex in
>> 3D.
>> > Can anyone give an example on how to use the constraint brick in python?
>> > Here is my obviously failed attempt:
>> >
>> > H = []; R = []
>> > b4 = gf.MdBrick("constraint", b2, 'eliminated');
>> >
>> > # Loop though all dof nodes looking for nodes satisfy the constraint
>> > criteria
>> > for dof in mfu.basic_dof_nodes():
>> > if (abs(dof[1] + 0.125) < 1e-6):
>> > # constrain the y component of dof to 0
>> > H.append([0,0,0,0,1,0,0,0,0]);
>> > R.append([0,0,0]);
>> > else:
>> > # dof is not part of the constraint.
>> > H.append([0,0,0,0,0,0,0,0,0]);
>> > R.append([0,0,0]);
>> > b4.constraints(H, R);
>> >
>> > Thank you very much!
>> > James
>>
>>
>> --
>>
>> Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
>> Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
>> 20, rue Albert Einstein
>> 69621 Villeurbanne Cedex, FRANCE
>> http://math.univ-lyon1.fr/~renard
>>
>> ---------
>>
>
>
_______________________________________________
Getfem-users mailing list
[email protected]
https://mail.gna.org/listinfo/getfem-users
