VolumePenalty.hpp

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#pragma once
 
#include <polyfem/assembler/GenericElastic.hpp>
#include <polyfem/assembler/MatParams.hpp>
 
namespace polyfem::assembler
{
    class VolumePenalty : public GenericElastic<VolumePenalty>
    {
    public:
        VolumePenalty();
 
        // sets material params
        void add_multimaterial(const int index, const json &params, const Units &units) override;
 
        std::string name() const override { return "VolumePenalty"; }
        std::map<std::string, ParamFunc> parameters() const override;
 
        template <typename T>
        T elastic_energy(
            const RowVectorNd &p,
            const double t,
            const int el_id,
            const DefGradMatrix<T> &def_grad) const
        {
            const double k = k_(p, t, el_id);
 
            const T J = polyfem::utils::determinant(def_grad);
            const T log_J = log(J);
 
            const T val = k / 2.0 * ((J * J - T(1)) / 2.0 - log_J);
 
            return val;
        }
 
    private:
        GenericMatParam k_;
    };
} // namespace polyfem::assembler