SmoothContactForm.cpp

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#include "SmoothContactForm.hpp"
 
#include <polyfem/utils/Logger.hpp>
#include <polyfem/utils/Types.hpp>
#include <polyfem/utils/Timer.hpp>
 
#include <ipc/barrier/adaptive_stiffness.hpp>
#include <ipc/utils/world_bbox_diagonal_length.hpp>
 
#include <cmath>
 
namespace polyfem::solver
{
    SmoothContactForm::SmoothContactForm(const ipc::CollisionMesh &collision_mesh,
                                         const double dhat,
                                         const double avg_mass,
                                         const double alpha_t,
                                         const double alpha_n,
                                         const bool use_adaptive_dhat,
                                         const double min_distance_ratio,
                                         const bool use_adaptive_barrier_stiffness,
                                         const bool is_time_dependent,
                                         const bool enable_shape_derivatives,
                                         const ipc::BroadPhaseMethod broad_phase_method,
                                         const double ccd_tolerance,
                                         const int ccd_max_iterations) : ContactForm(collision_mesh, dhat, avg_mass, use_adaptive_barrier_stiffness, is_time_dependent, enable_shape_derivatives, broad_phase_method, ccd_tolerance, ccd_max_iterations), params(dhat_, alpha_t, 0, alpha_n, 0, collision_mesh.dim() - 1), use_adaptive_dhat(use_adaptive_dhat), barrier_potential_(params)
    {
        params.set_adaptive_dhat_ratio(min_distance_ratio);
        if (use_adaptive_dhat)
        {
            collision_set_.compute_adaptive_dhat(collision_mesh, collision_mesh.rest_positions(), params, broad_phase_);
            if (use_adaptive_barrier_stiffness)
                logger().error("Adaptive dhat is not compatible with adaptive barrier stiffness");
        }
    }
 
    void SmoothContactForm::update_barrier_stiffness(const Eigen::VectorXd &x, const Eigen::MatrixXd &grad_energy)
    {
        if (!use_adaptive_barrier_stiffness())
            return;
 
        log_and_throw_error("Adaptive barrier stiffness not implemented for SmoothContactForm!");
    }
 
    void SmoothContactForm::update_collision_set(const Eigen::MatrixXd &displaced_surface)
    {
        // Store the previous value used to compute the constraint set to avoid duplicate computation.
        static Eigen::MatrixXd cached_displaced_surface;
        if (cached_displaced_surface.size() == displaced_surface.size() && cached_displaced_surface == displaced_surface)
            return;
 
        if (use_cached_candidates_)
            collision_set_.build(
                candidates_, collision_mesh_, displaced_surface, params, use_adaptive_dhat);
        else
            collision_set_.build(
                collision_mesh_, displaced_surface, params, use_adaptive_dhat, broad_phase_);
        cached_displaced_surface = displaced_surface;
    }
 
    double SmoothContactForm::value_unweighted(const Eigen::VectorXd &x) const
    {
        return barrier_potential_(collision_set_, collision_mesh_, compute_displaced_surface(x));
    }
 
    Eigen::VectorXd SmoothContactForm::value_per_element_unweighted(const Eigen::VectorXd &x) const
    {
        log_and_throw_error("value_per_element_unweighted not implemented!");
    }
 
    void SmoothContactForm::first_derivative_unweighted(const Eigen::VectorXd &x, Eigen::VectorXd &gradv) const
    {
        gradv = barrier_potential_.gradient(collision_set_, collision_mesh_, compute_displaced_surface(x));
        gradv = collision_mesh_.to_full_dof(gradv);
    }
 
    void SmoothContactForm::second_derivative_unweighted(const Eigen::VectorXd &x, StiffnessMatrix &hessian) const
    {
        // {
        //  io::OBJWriter::write(
        //      "collision_mesh.obj",
        //      compute_displaced_surface(x),
        //      collision_mesh_.edges(), collision_mesh_.faces());
        // }
        POLYFEM_SCOPED_TIMER("barrier hessian");
        hessian = barrier_potential_.hessian(collision_set_, collision_mesh_, compute_displaced_surface(x), project_to_psd_ ? ipc::PSDProjectionMethod::CLAMP : ipc::PSDProjectionMethod::NONE);
        hessian = collision_mesh_.to_full_dof(hessian);
    }
 
    void SmoothContactForm::post_step(const polysolve::nonlinear::PostStepData &data)
    {
        const Eigen::MatrixXd displaced_surface = compute_displaced_surface(data.x);
 
        const double curr_distance = collision_set_.compute_minimum_distance(collision_mesh_, displaced_surface);
        const double curr_active_distance = collision_set_.compute_active_minimum_distance(collision_mesh_, displaced_surface);
        if (!std::isinf(curr_distance))
        {
            const double ratio = sqrt(curr_distance) / dhat();
            const auto log_level = (ratio < 1e-6) ? spdlog::level::err : ((ratio < 1e-4) ? spdlog::level::warn : spdlog::level::debug);
            polyfem::logger().log(log_level, "Minimum distance during solve: {}, active distance: {}, dhat: {}", sqrt(curr_distance), sqrt(curr_active_distance), dhat());
        }
 
        if (data.iter_num == 0)
            return;
 
        if (use_adaptive_barrier_stiffness_)
        {
            if (is_time_dependent_)
            {
                const double prev_barrier_stiffness = barrier_stiffness();
 
                barrier_stiffness_ = ipc::update_barrier_stiffness(
                    prev_distance_, curr_distance, max_barrier_stiffness_,
                    barrier_stiffness(), ipc::world_bbox_diagonal_length(displaced_surface), 1e-7);
 
                if (barrier_stiffness() != prev_barrier_stiffness)
                {
                    polyfem::logger().debug(
                        "updated barrier stiffness from {:g} to {:g}",
                        prev_barrier_stiffness, barrier_stiffness());
                }
            }
            else
            {
                // TODO: missing feature
                // update_barrier_stiffness(data.x);
            }
        }
 
        prev_distance_ = curr_distance;
    }
} // namespace polyfem::solver