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Notes_on_the_SOFA_TetrahedronFEMForceField_class.md

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Notes on the SOFA TetrahedronFEMForceField class

This is the general purpose large strain co-rotational FEM model. It includes plastic deformation and per-element local stiffness.

These can be accessed via the Python API to animate a simulation. Internal attributes of the class

protected:

TetrahedronFEMForceField()

    : _mesh(NULL)

    , _indexedElements(NULL)

    , needUpdateTopology(false)

    , _initialPoints(initData(&_initialPoints, "initialPoints", "Initial Position"))

    , f_method(initData(&f_method,std::string("large"),"method","\"small\", \"large\" (by QR), \"polar\" or \"svd\" displacements"))

    , _poissonRatio(initData(&_poissonRatio,(Real)0.45f,"poissonRatio","FEM Poisson Ratio [0,0.5["))

    , _youngModulus(initData(&_youngModulus,"youngModulus","FEM Young Modulus"))

    , _localStiffnessFactor(initData(&_localStiffnessFactor, "localStiffnessFactor","Allow specification of different stiffness per element. If there are N element and M values are specified, the youngModulus factor for element i would be localStiffnessFactor[i*M/N]"))

    , _updateStiffnessMatrix(initData(&_updateStiffnessMatrix,false,"updateStiffnessMatrix",""))

    , _assembling(initData(&_assembling,false,"computeGlobalMatrix",""))

    , _plasticMaxThreshold(initData(&_plasticMaxThreshold,(Real)0.f,"plasticMaxThreshold","Plastic Max Threshold (2-norm of the strain)"))

    , _plasticYieldThreshold(initData(&_plasticYieldThreshold,(Real)0.0001f,"plasticYieldThreshold","Plastic Yield Threshold (2-norm of the strain)"))

    , _plasticCreep(initData(&_plasticCreep,(Real)0.9f,"plasticCreep","Plastic Creep Factor * dt [0,1]. Warning this factor depends on dt."))

    , _gatherPt(initData(&_gatherPt,"gatherPt","number of dof accumulated per threads during the gather operation (Only use in GPU version)"))

    , _gatherBsize(initData(&_gatherBsize,"gatherBsize","number of dof accumulated per threads during the gather operation (Only use in GPU version)"))

    , drawHeterogeneousTetra(initData(&drawHeterogeneousTetra,false,"drawHeterogeneousTetra","Draw Heterogeneous Tetra in different color"))

    , drawAsEdges(initData(&drawAsEdges,false,"drawAsEdges","Draw as edges instead of tetrahedra"))

    , _computeVonMisesStress(initData(&_computeVonMisesStress,0,"computeVonMisesStress","compute and display von Mises stress: 0: no computations, 1: using corotational strain, 2: using full Green strain"))

    , _vonMisesPerElement(initData(&_vonMisesPerElement, "vonMisesPerElement", "von Mises Stress per element"))

    , _vonMisesPerNode(initData(&_vonMisesPerNode, "vonMisesPerNode", "von Mises Stress per node"))

    , _vonMisesStressColors(initData(&_vonMisesStressColors, "vonMisesStressColors", "Vector of colors describing the VonMises stress"))

#ifdef SOFATETRAHEDRONFEMFORCEFIELD_COLORMAP

    , _showStressColorMap(initData(&_showStressColorMap,"showStressColorMap", "Color map used to show stress values"))

    , _showStressAlpha(initData(&_showStressAlpha, 1.0f, "showStressAlpha", "Alpha for vonMises visualisation"))

    , _showVonMisesStressPerNode(initData(&_showVonMisesStressPerNode,false,"showVonMisesStressPerNode","draw points  showing vonMises stress interpolated in nodes"))

#endif

    , isToPrint( initData(&isToPrint, false, "isToPrint", "suppress somes data before using save as function"))

    , _updateStiffness(initData(&_updateStiffness,false,"updateStiffness","udpate structures (precomputed in init) using stiffness parameters in each iteration (set listening=1)"))

{

    _poissonRatio.setRequired(true);

    _youngModulus.setRequired(true);

    _youngModulus.beginEdit()->push_back((Real)5000.);

    _youngModulus.endEdit();

    _youngModulus.unset();


    data.initPtrData(this);

    this->addAlias(&_assembling, "assembling");

    minYoung = 0.0;

    maxYoung = 0.0;