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OBJ model preparation

  • Copy motorBike tutorial:

    # cd $FOAM_RUN
    # cp -r $FOAM_TUTORIALS/incompressible/simpleFoam/motorBike ./
    # cd motorBike


    % writeFormat     ascii;
    % writePrecision  7;
  • OBJ surface model is copied from directory resources to directory constant/triSurface:

    # cp $FOAM_TUTORIALS/resources/geometry/motorBike.obj.gz \


  • Extract file using
    # gzip -d constant/triSurface/motorBike.obj.gz
  • View model in paraview:

    # paraview - -data=constant/triSurface/motorBike.obj

openfoam tutorial motor bike stl surface model

Figure: OpenFOAM tutorial motorbike, surface model

  • OBJ surface model can be checked using utility surfaceCheck:

    # cd constant/triSurface
    # surfaceCheck motorBike.obj > log.surfaceCheck 

  • It is possible to print out the number of illegal triangles:

    # grep 'illegal triangles' log.surfaceCheck

    Surface has 60941 illegal triangles. 
  • OBJ model has 60941 illegal triangles 
  • Look at the end of file log.surfaceCheck :
    # tail -16 log.surfaceCheck


    Number of unconnected parts : 4
    Splitting surface into parts ...
    Writing zoning to "zone_motorBike.vtk"...
    writing part 0 size 326215 to "motorBike_0.obj"
    writing part 1 size 1866 to "motorBike_1.obj"
    writing part 2 size 1876 to "motorBike_2.obj"
    writing part 3 size 1696 to "motorBike_3.obj"
    Number of zones (connected area with consistent normal) : 132055
    More than one normal orientation.


  • Four parts are unconnected


  • OpenFOAM supports following file formats:
    File extensionFormat description
    .ftrOpenFOAM triangulated format
    .stlStereolithography (STL), ASCII
    .stlbStereolithography (STL), binary
    .objWavefront object (OBJ)
    .off3D Object File Format (OFF)
    .vtkVisualisation Toolkit (VTK)
    .triTriangle format
    .acInivis AC3D
    .smeshTenGen surface mesh format
    .gtsMidas Geotechnical & Tunnel analysis System (GTS)
    .dxOpenDX format


  • Utility surfaceConvert converts formats e.g.:
    # surfaceConvert motorBike.obj motorBike.vtk


  • File format .vtk can be viewed in ParaView

openfoam tutorial motor bike surface model

Figure: OpenFOAM tutorial motorbike, vtk surface model