[petsc-users] Outputting cell data in stead of point data while writing .vtr file

[Smit Thijs]

Hi Matt,

Actually I have two 3D DMDA’s, one for the nodal data, where the FEM is solved on. The other DMDA is a cell centered one for the volume data, like the density of a particular voxel. Ideally I would like to write both point data (displacement field) and cell data (density) to the vtr.

Code for DMDA.

    DMBoundaryType bx = DM_BOUNDARY_NONE;
    DMBoundaryType by = DM_BOUNDARY_NONE;
    DMBoundaryType bz = DM_BOUNDARY_NONE;

    DMDAStencilType stype = DMDA_STENCIL_BOX;

PetscInt stencilwidth = 1;

    // Create the nodal mesh
    ierr = DMDACreate3d(PETSC_COMM_WORLD, bx, by, bz, stype, nx, ny, nz, PETSC_DECIDE, PETSC_DECIDE, PETSC_DECIDE,
                        numnodaldof, stencilwidth, 0, 0, 0, &(da_nodes));
    CHKERRQ(ierr);

    DMSetFromOptions(da_nodes);
    DMSetUp(da_nodes);

    ierr = DMDASetUniformCoordinates(da_nodes, xmin, xmax, ymin, ymax, zmin, zmax);
    CHKERRQ(ierr);

    ierr = DMDASetElementType(da_nodes, DMDA_ELEMENT_Q1);
    CHKERRQ(ierr);

Best, Thijs

From: Matthew Knepley <knepley at gmail.com>
Sent: 11 March 2021 14:08
To: Smit Thijs <thijs.smit at hest.ethz.ch>
Cc: petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] Outputting cell data in stead of point data while writing .vtr file

What kind of DM is it?

  Thanks,

     Matt

On Thu, Mar 11, 2021 at 3:36 AM Smit Thijs <thijs.smit at hest.ethz.ch<mailto:thijs.smit at hest.ethz.ch>> wrote:
Hi All,

I am outputting several vectors to a .vtr file successfully for viewing in Paraview. At this moment the information is written to point data. How can I change this and make sure the data is written to cell data?

The code I am currently using for outputting:

PetscViewer viewer;

ierr = PetscViewerVTKOpen(PETSC_COMM_WORLD, “test.vtr”, FILE_MODE_WRITE, &viewer);
CHKERRQ(ierr);

ierr = DMView(nd, viewer);
CHKERRQ(ierr);

PetscObjectSetName((PetscObject)xPhys,"xPhys");
ierr = VecView(xPhys, viewer);
CHKERRQ(ierr);

PetscObjectSetName((PetscObject)S,"SvonMises");
ierr = VecView(S, viewer);
CHKERRQ(ierr);

ierr = PetscViewerDestroy(&viewer);
CHKERRQ(ierr);

Best regards,

Thijs Smit

PhD Candidate
ETH Zurich
Institute for Biomechanics



--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/<http://www.cse.buffalo.edu/~knepley/>
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