This section covers the basic postprocessing when using oofem python bindings.

One can always directly access results using oofem API after solving each solution step. Another option consist of using existing or developing custom export module. OOFEM comes with many built-in export modules to produce output in desired format.

In the following sections, we will cover some techniques in more detail.

VTK postprocessing

This section illustrates how to query the data from oofem in python and use vtk library to visualize the results.


Here we will use pyvista python module ( to interface with Visualization toolkit (VTK). The recommended procedure to install pyvista is to use python package installer:

pip install pyvista

The approach uses built-in vtkmemory export module. This module allows in memory pythonic access to oofem grid data and variables. First, we use existing model. The model is read from input file and solved:

import oofempy
import numpy as np
import pyvista as pv

problem=oofempy.InstanciateProblem(dr, oofempy.problemMode.processor, False, None, False)

Next, we create instance of oofem vtkmemory export module and associate it to our problem. The constructor allows to filter the output to specific solution steps (here we use tstep_all=True to match all solution steps) and allows to select variables to export (we request dipslacement vector as primary variables, stress and strain tensors as internal variables and element number as cell variables, see oofem Input manual for details).

Further, the module is initialized and output is prepared.

vtkxmlPy = oofempy.vtkmemory(1, problem, domain_all=True, tstep_all=True, dofman_all=True, element_all=True, vars=(1,4), primvars=(1,), cellvars = (47,), stype=1, pythonExport=1)
vtkxmlPy.doOutput(problem.giveCurrentStep(), False)

The vtkmemory module allows in memory access to so called VTKPieces, objects representing piece (subset of mesh) to visualize. VTKPieces contain all needed information and data about piece geometry, connectivity and about exported variables. We start looping over the pieces, request data needed to instanciate pyvista UnstructuredGrid instance and attach exported variables to it.

for p in vtkxmlPy.getVTKPieces():
#p = vtkxmlPy.getVTKPieces()[0]
    print ("Piece:", p)
    disp = p.getPrimaryVertexValues(oofempy.UnknownType.DisplacementVector)
    sig = p.getInternalVertexValues(oofempy.InternalStateType.IST_StressTensor)
    sigx = sig[:, 0]

    grid = pv.UnstructuredGrid(p.getCellConnectivity(), p.getCellTypes(vtkxmlPy), p.getVertices())
    grid.point_arrays['Sigma_xx'] = sigx
    grid['Disp'] = disp
    warped = grid.warp_by_vector('Disp', factor=1000.)
    p = pv.Plotter()
    p.add_mesh(warped, scalars='Sigma_xx')
    p.add_mesh(grid, style='wireframe', color='black')

You can follow for a full example.