Methods

{
  "name": "MechanicalGetConstraintInfoVisitor",
  "namespace": "sofa::simulation::mechanicalvisitor",
  "module": "Sofa.framework.Simulation.Core",
  "include": "sofa/simulation/mechanicalvisitor/MechanicalGetConstraintInfoVisitor.h",
  "doc": "",
  "inherits": [
    "BaseMechanicalVisitor"
  ],
  "templates": [],
  "data_fields": [],
  "links": [],
  "methods": [
    {
      "name": "fwdConstraintSet",
      "return_type": "Result",
      "params": [
        {
          "name": "node",
          "type": "simulation::Node *"
        },
        {
          "name": "cSet",
          "type": "core::behavior::BaseConstraintSet *"
        }
      ],
      "is_virtual": true,
      "is_pure_virtual": false,
      "is_static": false,
      "access": "public"
    },
    {
      "name": "stopAtMechanicalMapping",
      "return_type": "bool",
      "params": [
        {
          "name": "",
          "type": "simulation::Node *"
        },
        {
          "name": "",
          "type": "core::BaseMapping *"
        }
      ],
      "is_virtual": true,
      "is_pure_virtual": false,
      "is_static": false,
      "access": "public"
    }
  ],
  "description": "The `MechanicalGetConstraintInfoVisitor` is a visitor component in the SOFA framework, designed to collect constraint information from mechanical systems during simulation. It inherits from `BaseMechanicalVisitor`, indicating its role in traversing and interacting with mechanical nodes within the scene graph.\n\n### Role and Purpose:\nThis component facilitates the extraction of constraint-related data by visiting different parts of the mechanical system. The collected constraints are essential for solving constrained dynamics problems, such as those involving Lagrange multipliers or penalty methods. It is particularly useful in scenarios where detailed information about the active constraints needs to be gathered.\n\n### Interactions with Other Components:\nThe `MechanicalGetConstraintInfoVisitor` interacts primarily through its virtual method `fwdConstraintSet`, which allows it to collect constraint information from nodes and BaseConstraintSets within the scene graph. This interaction is critical for maintaining consistency in mechanical simulations involving constraints. The visitor does not stop at mechanical mappings, as indicated by the override of `stopAtMechanicalMapping` returning `false`. This ensures that all parts of the mechanical hierarchy are visited.\n\n### Practical Usage and Data Fields:\nThe constructor accepts parameters such as `core::ConstraintParams`, a vector for constraint block information (`VecConstraintBlockInfo`), and a vector for persistent IDs (`VecPersistentID`). These fields allow the visitor to store and process constraints during its traversal. The method `fwdConstraintSet` is responsible for gathering this constraint data from Lagrangian constraints, while maintaining timing information through the `begin` and `end` methods.\n\nThis component is typically used internally within SOFA's mechanical simulation pipeline to ensure that all relevant constraint information is collected before performing numerical integration or solving systems of equations.",
  "maths": "### Mathematical and Physical Description\n\nThe `MechanicalGetConstraintInfoVisitor` is a visitor component in the SOFA framework designed to collect constraint information from mechanical systems during simulation. This component plays an essential role in ensuring that all relevant constraints are gathered for solving constrained dynamics problems, such as those involving Lagrange multipliers or penalty methods.\n\n#### Governing Equations and Operators\nThe `MechanicalGetConstraintInfoVisitor` does not directly implement governing equations or operators like the mass matrix $M$, stiffness matrix $K$, internal force $f_{int}$, or residual $R$. Instead, it is responsible for gathering constraint information from different parts of the mechanical system. The constraints collected can be part of a broader Lagrangian mechanics formulation where the constraints are enforced through Lagrange multipliers.\n\nFor example, in the context of constrained dynamics, if the Lagrangian $\boldsymbol{\text{L}}$ is augmented with penalty terms for constraints:\n\n\begin{equation}\n\\mathcal{L} = T - V + \\sum_i λ_i c_i(\\mathbf{x}, t)\n\tag{1}\n\text{where: }\nλ_i \text{ are the Lagrange multipliers and } c_i(\\mathbf{x}, t) \text{ are the constraint equations.}\n\text{The Euler-Lagrange equation for such a system becomes:}\n\frac{∂}{∂t} \\left(\frac{∂ \boldsymbol{\text{L}}}{∂ ņ̇_i}\right) - \frac{∂ \boldsymbol{\text{L}}}{∂ ņ_i} + λ_i \frac{∂ c_i}{∂ ņ_i} = 0\n\tag{2}\n\text{where } ņ_i \text{ are the generalized coordinates.}\n\tag{3}\n\text{The Lagrange multipliers } λ_i \text{ can be determined by enforcing constraint equations:}\nc_i(ņ, t) = 0\n\tag{4}\n\\end{equation}\n\n#### Constitutive or Kinematic Laws Involved\nThe `MechanicalGetConstraintInfoVisitor` does not directly involve constitutive laws (e.g., strain measures, stress tensors, hyperelastic potentials), kinematic models, or damping models. Its primary function is to collect information about constraints, which are typically expressed as equations of the form $c_i(ņ, t) = 0$.\n\n#### Role in the Global FEM Pipeline\nThe `MechanicalGetConstraintInfoVisitor` fits into the broader variational/Lagrangian mechanics framework by ensuring that all relevant constraint information is gathered before numerical integration or solving systems of equations. It plays a critical role during the assembly phase, where constraints are integrated into the overall system.\n\n#### Numerical Methods and Discretization Choices\nThe `MechanicalGetConstraintInfoVisitor` does not directly encode any specific numerical methods or discretization choices. Instead, it facilitates the collection of constraint information from different parts of the mechanical system using a visitor pattern. This ensures that all relevant constraints are included in the overall simulation.\n\n#### Fit into Variational / Lagrangian Mechanics Framework\nThe `MechanicalGetConstraintInfoVisitor` is part of the broader SOFA framework's approach to enforcing constraints within variational and Lagrangian mechanics formulations. By collecting constraint information, it supports the enforcement of constraints through methods like Lagrange multipliers or penalty terms in the overall simulation pipeline.\n",
  "abstract": "The `MechanicalGetConstraintInfoVisitor` collects constraint information from mechanical systems during simulation, facilitating the enforcement of constraints in Lagrangian mechanics formulations.",
  "sheet": "# MechanicalGetConstraintInfoVisitor\n\n## Overview\nThe `MechanicalGetConstraintInfoVisitor` is a visitor component that gathers constraint-related data by traversing and interacting with mechanical nodes within the SOFA scene graph. It inherits from `BaseMechanicalVisitor`, indicating its role in collecting constraints essential for solving constrained dynamics problems involving Lagrange multipliers or penalty methods.\n\n## Parameters and Data\nThe constructor accepts parameters such as `core::ConstraintParams`, a vector for constraint block information (`VecConstraintBlockInfo`), and a vector for persistent IDs (`VecPersistentID`). These fields allow the visitor to store and process constraints during its traversal. The method `fwdConstraintSet` is responsible for gathering this constraint data from Lagrangian constraints, while maintaining timing information through the `begin` and `end` methods.\n\n## Dependencies and Connections\nThe `MechanicalGetConstraintInfoVisitor` interacts primarily through its virtual method `fwdConstraintSet`, which allows it to collect constraint information from nodes and BaseConstraintSets within the scene graph. This interaction is critical for maintaining consistency in mechanical simulations involving constraints. The visitor does not stop at mechanical mappings, as indicated by the override of `stopAtMechanicalMapping` returning `false`. This ensures that all parts of the mechanical hierarchy are visited."
}