[petsc-users] coordinates of vertices of a cell in 3D DMPlex

[Mark Adams]

I get all the coordinates with this method:

static PetscErrorCode crd_func(PetscInt dim, PetscReal time, const
PetscReal x[], PetscInt Nf_dummy, PetscScalar *u, void *actx)
{
  int i;
  PetscFunctionBeginUser;
  for (i = 0; i < dim; ++i) u[i] = x[i];
  PetscFunctionReturn(0);
}

  PetscErrorCode (*initu[1])(PetscInt, PetscReal, const PetscReal [],
PetscInt, PetscScalar [], void *);
  /* project coordinates to vertices */
  ierr = DMCreateGlobalVector(crddm, &crd_vec);CHKERRV(ierr);
  initu[0] = crd_func;
  ierr = DMProjectFunction(crddm, 0.0, initu, NULL, INSERT_ALL_VALUES,
crd_vec);CHKERRV(ierr);
  ierr = VecViewFromOptions(crd_vec, NULL, "-coord_view");CHKERRV(ierr);
  /* iterate over mesh data and get indices */
  ierr = VecGetArrayRead(crd_vec,&xx);CHKERRV(ierr);
  ierr = VecGetLocalSize(rho,&N);CHKERRV(ierr);
  /* access grid data here */
  for (p=0;p<N;p++) {
    for (i=0;i<dim;i++) ..... = xx[p*dim+i];
    PetscPrintf(PETSC_COMM_SELF,"xx = (%g, %g)\n", xx[p*dim+0],
xx[p*dim+1]);
  }
  ierr = VecRestoreArrayRead(crd_vec,&xx);CHKERRV(ierr);
  ierr = VecDestroy(&crd_vec);CHKERRV(ierr);

On Sat, Jul 25, 2020 at 4:10 AM Swarnava Ghosh <swarnava89 at gmail.com> wrote:

> Dear Petsc users,
>
> I had a trivial question about DMPlex. Suppose I have a 3D mesh of
> tetrahedrons. I want to find out the 3D coordinates of the vertices of a
> particular cell. What would be the function to do this?
>
> Thank you,
> SG
>
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