HookeLinearElasticity.hpp

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#pragma once
 
#include <polyfem/assembler/Assembler.hpp>
#include <polyfem/assembler/MatParams.hpp>
#include <polyfem/utils/AutodiffTypes.hpp>
#include <polyfem/utils/ElasticityUtils.hpp>
 
// local assembler for HookeLinearElasticity C : (F+F^T)/2, see linear elasticity
namespace polyfem::assembler
{
    class HookeLinearElasticity : public LinearAssembler, NLAssembler, ElasticityAssembler
    {
    public:
        using LinearAssembler::assemble;
        using NLAssembler::assemble_energy;
        using NLAssembler::assemble_gradient;
        using NLAssembler::assemble_hessian;
 
        HookeLinearElasticity();
 
        // res is R^{dim²}
        Eigen::Matrix<double, Eigen::Dynamic, 1, 0, 9, 1>
        assemble(const LinearAssemblerData &data) const override;
 
        // compute elastic energy
        double compute_energy(const NonLinearAssemblerData &data) const override;
        // neccessary for mixing linear model with non-linear collision response
        Eigen::MatrixXd assemble_hessian(const NonLinearAssemblerData &data) const override;
        // compute gradient of elastic energy, as assembler
        Eigen::VectorXd assemble_gradient(const NonLinearAssemblerData &data) const override;
 
        VectorNd compute_rhs(const AutodiffHessianPt &pt) const override;
 
        void set_size(const int size) override;
 
        // sets the elasticty tensor
        void add_multimaterial(const int index, const json &params, const Units &units) override;
 
        const ElasticityTensor &elasticity_tensor() const { return elasticity_tensor_; }
 
        virtual bool is_linear() const override { return true; }
        bool allow_inversion() const override { return true; }
        std::string name() const override { return "HookeLinearElasticity"; }
        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:
        ElasticityTensor elasticity_tensor_;
 
        // aux function that computes energy
        // double compute_energy is the same with T=double
        // assemble_gradient is the same with T=DScalar1 and return .getGradient()
        template <typename T>
        T compute_energy_aux(const NonLinearAssemblerData &data) const;
    };
} // namespace polyfem::assembler