Thanks. The reason why I need xyz of the DOFs is that my system matrices are solved by an eigenvalue solver outside libmesh and the size of the eigenvector solution produced by the solver equals to the dimension of the system matrices (or DOFs). I'd like to plot the eigenvector solutions, thus I need to the correspondent xyz coordinates of each of the eigenvector value for visualization purpose.
It was easy to do for the 2nd order Lagrange because the size of the eigenvector = n_nodes, now I'm stuck at plotting the results from 3rd order hermite, which have much better accuracy.
On Wed, 26 Jul 2006, David Xu wrote:
> After I used 3rd order hermite shape function, I realized the resulting
> dimension of the assembled system matrices is not equal to the number of
> mesh nodes as in the case of using 2nd order Lagrange. The dimension equals
> the number of DOFs. I was wondering how to get xyz physical location of each
> of the global DOF points. Is there an iterator available like the one for
> mesh nodes?
No, there isn't. If you want to be dangerous, you can use the
DOFObject interface of a node in the mesh of an initialized
EquationSystems to view every global degree of freedom index on that
node. Keep in mind that for many elements (including the HERMITE
elements for p=4 and above, I think) there are also degrees of freedom
associated with the Elem itself.
Why do you need the physical location of non-Lagrange degrees of
freedom? That's kind of unusual.