InversionBarrier.hpp

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#pragma once
 
#include <polyfem/assembler/Assembler.hpp>
#include <polyfem/assembler/MatParams.hpp>
 
// Standalone inversion barrier, split out of the former ModifiedNeoHookeanElasticity
// (ported from the original positive-jacobian branch, commit c59afca4, later reverted
// in 342cb860) so it can be combined with any elasticity model via SumModel/MaterialSum.
namespace polyfem::assembler
{
    class InversionBarrier : public ElasticityNLAssembler
    {
    public:
        InversionBarrier();
 
        using ElasticityNLAssembler::assemble_energy;
        using ElasticityNLAssembler::assemble_gradient;
        using ElasticityNLAssembler::assemble_hessian;
 
        double compute_energy(const NonLinearAssemblerData &data) const override;
        Eigen::VectorXd assemble_gradient(const NonLinearAssemblerData &data) const override;
        Eigen::MatrixXd assemble_hessian(const NonLinearAssemblerData &data) const override;
 
        VectorNd compute_rhs(const AutodiffHessianPt &pt) const override;
 
        void add_multimaterial(const int index, const json &params, const Units &units, const std::string &root_path) override;
 
        std::string name() const override { return "InversionBarrier"; }
        bool allow_inversion() const override { return false; }
        std::map<std::string, ParamFunc> parameters() const override;
 
        void assign_stress_tensor(const OutputData &data,
                                  const int all_size,
                                  const ElasticityTensorType &type,
                                  Eigen::MatrixXd &all,
                                  const std::function<Eigen::MatrixXd(const Eigen::MatrixXd &)> &fun) const override;
 
    private:
        LameParameters params_;
        // Activation threshold for the barrier: zero for J >= JBarrierThreshold, diverges to +inf as J -> 0.
        GenericMatParam JBarrierThreshold_;
    };
} // namespace polyfem::assembler