SceneLoaderPHP
The `SceneLoaderPHP` loads simulation scenes defined by PHP scripts or `.pscn` files into the SOFA framework, enabling users to leverage PHP for defining complex simulation scenarios.
- module
- Sofa.framework.Simulation.Common
- namespace
- sofa::simulation
- include
- sofa/simulation/common/SceneLoaderPHP.h
- inherits
-
- SceneLoader
- description
The MeshSpringForceField in the SOFA framework is a force field that simulates spring forces acting along the edges of a mesh. It contributes to the internal force vector wzxhzdk:3, which represents the elastic and damping forces within the deformed solid. The governing equations for this component can be described as follows:
Governing Equations
Internal Force Contribution (wzxhzdk:4)
The MeshSpringForceField computes the internal force contributions from springs defined along the edges of mesh elements such as lines, triangles, quads, tetrahedra, and cubes. The internal forces are given by:
egin{equation}
\mathbf{f}^{e}_{int}(\mathbf{x}) = -k_s (|\mathbf{l}|_0 - |\mathbf{l}|) \frac{\mathbf{l}}{|\mathbf{l}|} + c_d \dot{\mathbf{l}},
ag{1}
ext{(Hooke's Law and Damping)}
ext{
where
- wzxhzdk:8 is the stiffness coefficient for a given edge,
- wzxhzdk:9 is the damping coefficient for that edge,
- wzxhzdk:10 is the length of the edge defined by two nodes, and
- wzxhzdk:11 is the rest length (initial undeformed length) of that edge.
}
ag{2}
ext{(Elongation Term)}
ext{
If the component is configured with noCompression set to true, forces are only considered for elongations. This means the internal force vector will be zero if wzxhzdk:12. }
Constitutive Laws and Kinematic Measures
The spring model used by MeshSpringForceField is a simple linear elastic relationship based on Hooke's Law, which states that the force exerted by a spring is proportional to its elongation or compression from an equilibrium position. The damping term is also linearly related to the relative velocity of the nodes.
The strain measure used here is effectively the ratio of the current edge length wzxhzdk:5 to its rest length wzxhzdk:6. For small deformations, this can be approximated by a linear strain measure, but it remains applicable for large deformations as well since it directly measures the change in distance between nodes.
Role in FEM Pipeline
In the broader context of the FEM pipeline, MeshSpringForceField contributes to the internal force vector wzxhzdk:7 during the assembly phase. This component:
Numerical Methods and Discretization Choices
The MeshSpringForceField discretizes the spring forces along the edges of mesh elements, where each edge is modeled as a simple linear spring with optional damping. The stiffness and damping coefficients can be set differently for different types of mesh elements (lines, triangles, quads, tetrahedra, cubes).
The
init method initializes these springs by accessing connectivity data from the topology container. It ensures that springs are only added if their nodes lie within a specified local range, which is useful for parallel computations.Variational and Lagrangian Mechanics Framework
Within the variational mechanics framework of SOFA, MeshSpringForceField can be seen as providing a discrete approximation to the potential energy wzxhzdk:16 in the Lagrangian formulation:
egin{equation}
\mathcal{L}(q,\dot q) = T(q,\dot q) - V(q),
ag{3}
ext{(Lagrangian Formulation)}
where wzxhzdk:17 includes the potential energy stored in the springs. The internal force vector wzxhzdk:18 is derived from this potential energy via the principle of virtual work, ensuring consistency with variational principles.
Within the variational mechanics framework of SOFA, MeshSpringForceField can be seen as providing a discrete approximation to the potential energy wzxhzdk:13 in the Lagrangian formulation:
egin{equation}
\mathcal{L}(q,\dot q) = T(q,\dot q) - V(q),
ag{3}
ext{(Lagrangian Formulation)}
where wzxhzdk:14 includes the potential energy stored in the springs. The internal force vector wzxhzdk:15 is derived from this potential energy via the principle of virtual work, ensuring consistency with variational principles.
Summary
In summary, MeshSpringForceField implements a simple but effective model for simulating elastic and dissipative forces within deformable solids by discretizing the solid into springs along mesh edges. It is grounded in Lagrangian mechanics, contributes to the global force vector wzxhzdk:19, and plays a crucial role in the nonlinear solution process of FEM simulations.
Methods
bool
canLoadFileExtension
(const char * extension)
virtual
sofa::simulation::NodeSPtr
doLoad
(const int & filename, const int & sceneArgs)
virtual
int
getFileTypeDesc
()
void
getExtensionList
(ExtensionList * list)
virtual
{
"name": "SceneLoaderPHP",
"namespace": "sofa::simulation",
"module": "Sofa.framework.Simulation.Common",
"include": "sofa/simulation/common/SceneLoaderPHP.h",
"doc": "",
"inherits": [
"SceneLoader"
],
"templates": [],
"data_fields": [],
"links": [],
"methods": [
{
"name": "canLoadFileExtension",
"return_type": "bool",
"params": [
{
"name": "extension",
"type": "const char *"
}
],
"is_virtual": true,
"is_pure_virtual": false,
"is_static": false,
"access": "public"
},
{
"name": "doLoad",
"return_type": "sofa::simulation::NodeSPtr",
"params": [
{
"name": "filename",
"type": "const int &"
},
{
"name": "sceneArgs",
"type": "const int &"
}
],
"is_virtual": true,
"is_pure_virtual": false,
"is_static": false,
"access": "public"
},
{
"name": "getFileTypeDesc",
"return_type": "int",
"params": [],
"is_virtual": false,
"is_pure_virtual": false,
"is_static": false,
"access": "public"
},
{
"name": "getExtensionList",
"return_type": "void",
"params": [
{
"name": "list",
"type": "ExtensionList *"
}
],
"is_virtual": true,
"is_pure_virtual": false,
"is_static": false,
"access": "public"
}
],
"description": "The `SceneLoaderPHP` component in SOFA is designed to load simulation scenes from PHP (`.php`, `.pscn`) files. It inherits from the generic `SceneLoader` class and implements methods for checking file extensions, loading scene files, and providing descriptions of file types. This loader facilitates the integration of scene definitions written in PHP into the SOFA framework.\n\n### Role and Purpose:\n- **Role**: The primary role is to interpret and load simulation scenes defined by PHP scripts or `.pscn` files, translating them into a form usable within the SOFA scene graph structure.\n- **Purpose**: Enables users to leverage PHP for defining complex simulation scenarios, which can then be executed using SOFA's powerful simulation capabilities.\n\n### Interactions with Other Components:\n- **SceneLoaderFactory**: Registered in the `SceneLoaderFactory` to facilitate dynamic loading of scenes from specific file types.\n- **NodeElement and SceneLoaderXML**: Utilizes these components for processing and interpreting the loaded scene data, converting PHP-generated content into a format suitable for SOFA simulation nodes.\n\n### Practical Usage Guidance:\n- Ensure that PHP is installed in your environment to use this loader. The component attempts to locate `php.exe` on Windows or `php` on other systems via the PATH environment variable.\n- Use the `doLoad` method to load scenes from specified files, handling both `.php` and `.pscn` extensions.\n\n### Data Fields:\n- This component does not define any specific data fields. It primarily relies on inherited methods and dynamically generated scene content.",
"maths": "The `SceneLoaderPHP` component in the SOFA framework is designed to load simulation scenes from files written in PHP (`.php`, `.pscn`). This component does not directly contribute to any specific governing equations or operators related to finite element methods (FEM), constitutive laws, kinematics, or numerical methods. Instead, it acts as an interface for integrating scene definitions generated by external scripts into the SOFA simulation environment.\n\n### Mathematical and Physical Description:\n\n1. **Governing Equations/Operators**:\n - The `SceneLoaderPHP` does not implement any governing equations or operators directly relevant to FEM, such as mass matrix (\\( M \")), stiffness matrix (\\( K \")), internal force vector (\\( f_{int} \")), residual vector (\\( R \")), etc.\n\n2. **Constitutive or Kinematic Laws**:\n - The component does not define any constitutive laws (e.g., stress-strain relationships), kinematics, strain measures, hyperelastic potentials, damping models, constraint Jacobians, or other physical properties directly associated with FEM simulation.\n\n3. **Role in the Global FEM Pipeline**:\n - This component is primarily involved in the initial step of loading a scene definition from an external file format (PHP). It does not participate in assembly, time integration, nonlinear solve, linear solve, constraint handling, or mappings directly related to the FEM simulation pipeline.\n\n4. **Numerical Methods/Discretization Choices**:\n - The `SceneLoaderPHP` is concerned with translating scene definitions from PHP into a form that can be used within SOFA's internal structures (nodes, objects, forces, etc.). It does not encode any specific numerical methods or discretization choices related to FEM simulation.\n\n5. **Fit into Variational/Lagrangian Mechanics Framework**:\n - The component facilitates the loading of scenes but does not have a direct role in the variational principles (e.g., action principle, Euler-Lagrange equations), Lagrangian mechanics formulations (kinetic and potential energy terms), or any other theoretical aspects related to FEM simulation.\n\n### Summary:\n- The `SceneLoaderPHP` is an input/output component used for loading scenes from PHP-generated files into the SOFA framework. It does not contribute directly to mathematical or physical models relevant to finite element analysis. Instead, it focuses on ensuring that scene definitions can be integrated seamlessly into the simulation environment.",
"abstract": "The `SceneLoaderPHP` loads simulation scenes defined by PHP scripts or `.pscn` files into the SOFA framework, enabling users to leverage PHP for defining complex simulation scenarios.",
"sheet": "# SceneLoaderPHP\n\n## Overview\n\nThe `SceneLoaderPHP` component is an input/output component that inherits from the generic `SceneLoader` class. It facilitates loading scenes defined by PHP scripts or `.pscn` files into the SOFA framework, allowing users to define complex simulation scenarios using PHP.\n\n## Dependencies and Connections\n\nThis component typically requires integration with the `SceneLoaderFactory`, which registers it for dynamic scene loading from specific file types. The loaded scene data is processed and interpreted by components such as `NodeElement` and `SceneLoaderXML`, converting PHP-generated content into a format suitable for SOFA simulation nodes."
}