Segmentation fault error with AddFixedConstraint()

Question

I want to make composite object by attaching a deformable object(pipe) to a cylinder object. But it fails when AddFixedConstraint() function is called with a "Segmentation fault" error as below.

[2024-02-19 00:26:09.610] [console] [warning] DRAKE DEPRECATED: Use MultibodyPlantConfig::discrete_contact_approximation instead of MultibodyPlantConfig::discrete_contact_solver. The deprecated code will be removed from Drake on or after 2024-04-01.
HEY
Segmentation fault (core dumped)

"HEY" is what I printed to see that my code cannot pass through the AddFixedConstraint() function.

Following is my code:

///////////////////////
    /// Configure Plant ///
    ///////////////////////
    drake::systems::DiagramBuilder<double> builder;

    MultibodyPlantConfig plant_config;
    plant_config.time_step = time_step;
    plant_config.discrete_contact_solver = "sap";

    auto [plant, scene_graph] = AddMultibodyPlant(plant_config, &builder);

    
    //////////////////////////
    /// SETUP PLANE GROUND ///
    //////////////////////////
    ProximityProperties rigid_proximity_props;
    const CoulombFriction<double> surface_friction(1.15, 1.15);
    AddContactMaterial({}, {}, surface_friction, &rigid_proximity_props);
    rigid_proximity_props.AddProperty(drake::geometry::internal::kHydroGroup, drake::geometry::internal::kRezHint, 1.0);

    Box ground{2, 2, 2};
    const RigidTransformd X_WG(Eigen::Vector3d{0, 0, -1});
    plant.RegisterCollisionGeometry(plant.world_body(), X_WG, ground, "ground_collision", rigid_proximity_props);
    IllustrationProperties illustration_props;
    illustration_props.AddProperty("phong", "diffuse", Vector4d(0.7, 0.5, 0.4, 0.8));
    plant.RegisterVisualGeometry(plant.world_body(), X_WG, ground, "ground_visual", std::move(illustration_props));


    ///////////////////////////////
    /// SETUP DEFORMABLE OBJECT ///
    ///////////////////////////////
    auto owned_deformable_model = std::make_unique<DeformableModel<double>>(&plant);
    // DeformableModel<double> owned_deformable_model(&plant);

    DeformableBodyConfig<double> deformable_config;
    deformable_config.set_youngs_modulus(E);
    deformable_config.set_poissons_ratio(nu);
    deformable_config.set_mass_density(density);
    deformable_config.set_stiffness_damping_coefficient(stiffness_beta);

    const std::string deformable_vtk = "{MY WORKSPACE PATH}/src/drake_controller/resource/pipe.vtk";
    const double scale = 0.01; // 0.65
    auto deformable_mesh = std::make_unique<Mesh>(deformable_vtk, scale);
    const double kL = 0.09 * scale;

    // const RigidTransformd X_WB(Vector3<double>(0.0, 0.0, kL / 2.0));
    const RigidTransformd X_WB(drake::Vector3<double>(0.0, 0.0, 0.0));
    auto torus_instance = std::make_unique<GeometryInstance>( X_WB, std::move(deformable_mesh), "deformable_object");

    /* Minimumly required proximity properties for deformable bodies: A valid Coulomb friction coefficient. */
    ProximityProperties deformable_proximity_props;
    AddContactMaterial({}, {}, surface_friction, &deformable_proximity_props);
    torus_instance->set_proximity_properties(deformable_proximity_props);

    /* Registration of all deformable geometries ostensibly requires a resolution
    hint parameter that dictates how the shape is tessellated. In the case of a
    `Mesh` shape, the resolution hint is unused because the shape is already
    tessellated. */
    const double unused_resolution_hint = 1.0;
    auto deformable_body_id = owned_deformable_model->RegisterDeformableBody(std::move(torus_instance), deformable_config, unused_resolution_hint);
    DeformableModel<double>* deformable_model = owned_deformable_model.get();
    
    plant.AddPhysicalModel(std::move(owned_deformable_model));

    //////////////////////////
    /// SETUP RIGID OBJECT ///
    //////////////////////////
    Parser parser(&plant);

    auto peg_idx = parser.AddModels("{MY WORKSPACE PATH}/src/drake_controller/resource/1mm_cylinder.sdf");
    const drake::multibody::RigidBody<double>& peg_body = plant.GetBodyByName("cylinder_body");
    const drake::multibody::Frame<double>& peg_frame = plant.GetFrameByName("cylinder_top_center");

    RigidTransformd W_X_PEG(Eigen::Vector3d{0,0,0});
    plant.SetDefaultFreeBodyPose(peg_body, W_X_PEG);
    AddFloatingRpyJoint(&plant, const_cast<drake::multibody::RigidBodyFrame<double>&>(peg_frame.body().body_frame()), peg_idx.at(0));

    drake::math::RigidTransform<double> RIGID_X_DEFORMABLE(drake::Vector3<double>(0,0,0.02));
    drake::math::RigidTransform<double> RIGID_X_GEOMETRY;
    drake::geometry::Cylinder peg_mesh(0.048,0.04);
    drake::geometry::Shape* peg_shape = peg_mesh.Clone().get();
    std::cout << "HEY" << std::endl;
    auto multibody_constraint_id = deformable_model->AddFixedConstraint(deformable_body_id, peg_body, RIGID_X_DEFORMABLE, *peg_shape, RIGID_X_GEOMETRY.SetIdentity());
    // std::cout << multibody_constraint_id << std::endl;
    std::cout << "HEY" << std::endl;

    ////////////////////////////////////
    /// FINALIZE OBJECT REGISTRATION ///
    ////////////////////////////////////
    plant.set_gravity_enabled(peg_idx.at(0), false);
    plant.Finalize();

I checked exception cases, except last case, described in the c++ documentation: text

1. std::exception if no deformable body with the given body_A_id has been registered.
2. std::exception unless body_B is registered with the same multibody plant owning this deformable model.
3. std::exception if shape is not supported by QueryObject::ComputeSignedDistanceToPoint(). Currently, supported shapes include Box, Capsule, Cylinder, Ellipsoid, HalfSpace, and Sphere.
4. std::exception if Finalize() has been called on the multibody plant owning this deformable model.
5. std::exception if no constraint is added (i.e. no vertex of the deformable body is inside the given shape with the given poses).

Thanks in advance!

Answer 1

As Igor Tandetnik pointed out, peg_shape ends up as a dangling pointer resulting in your segfault. Not sure why you have the Clone() though in the first place. You should just be passing peg_mesh to AddFixedConstraint():

auto multibody_constraint_id = deformable_model->AddFixedConstraint(deformable_body_id, peg_body, RIGID_X_DEFORMABLE, peg_mesh, RIGID_X_GEOMETRY.SetIdentity());