How to implement an animation model different from the visual model ?

Screenshot : the liver - visual model - immersing in one tetrahedron - the animation model.

The code

The code relative to this example is located in : sofa/applications/tutorials/oneTetrahedron

There is just a Main.cpp with less than 100 lines. Open and observe it.

• See HowToCompileATutorial to run it.
• See OneParticule tutorial to know how to manipulate the interface.

The scene graph

The scene graph used for this example

• See OneParticule tutorial to know how to get this graph in SOFA

More comments

• The graph root node:

  sofa::simulation::tree::GNode* groot = new sofa::simulation::tree::GNode;
  ...
  

• One solver for all the graph

  sofa::component::odesolver::CGImplicitSolver* solver =
      new sofa::component::odesolver::CGImplicitSolver;
  ...
  

• Set gravity for all the graph

  sofa::component::context::Gravity* gravity =
      new sofa::component::context::Gravity;
  ...
  

• Tetrahedron degrees of freedom: set the geometric values of the 4 vertices

  sofa::component::MechanicalObject<MyTypes>* DOF =
      new sofa::component::MechanicalObject<MyTypes>;
  ...
  

• Tetrahedron uniform mass: set an uniform mass onto the tetrahedron

  sofa::component::mass::UniformMass<MyTypes,double>* mass =
      new sofa::component::mass::UniformMass<MyTypes,double>;
  ...
  

• Tetrahedron topology: the tetrahedron itself

  sofa::component::topology::MeshTopology* topology =
      new sofa::component::topology::MeshTopology;
  ...
  

• Tetrahedron constraints: fixe the tetrahedron on the top

  sofa::component::constraint::FixedConstraint<MyTypes>*
  constraints =
      new sofa::component::constraint::FixedConstraint<MyTypes>;
  ...
  

• Tetrahedron force field, the animation model : simulate the tetrahedron as a deformable FEM element

  sofa::component::forcefield::TetrahedronFEMForceField<MyTypes>* fem =
      new sofa::component::forcefield::TetrahedronFEMForceField<MyTypes>;
  ...
  

• Tetrahedron skin: a children node containing the liver

  sofa::simulation::tree::GNode* skin = new sofa::simulation::tree::GNode;
  ...
  

• The visual model: the liver

  sofa::component::visualmodel::OglModel* visual
      = new sofa::component::visualmodelOglModel;
  visual->load("../../../scenes/VisualModels/liver-smooth.obj", "", "");
  

• The mapping between the tetrahedron (DOF) and the liver (visual) in order that the liver follow the tetrahedron animation

  MyMapping* mapping = new MyMapping(DOF, visual);
  ...
  

The mapping type between the visual and animation models

Here a BarycentricMapping is used to map the visual model to the animation model. This type is templated and you can find some examples of uses at the end of the file sofa/modules/sofa/component/mapping/BarycentricMapping.cpp

By analogy, we have built MyMapping type :

typedef sofa::component::mapping::BarycentricMapping<
    sofa::core::Mapping<
        sofa::core::componentmodel::behavior::MechanicalModel<MyTypes>,
        sofa::core::componentmodel::behavior::MappedModel< 
            sofa::defaulttype::ExtVectorTypes< 
                sofa::defaulttype::Vec<3,GLfloat>,
                sofa::defaulttype::Vec<3,GLfloat>
            >
        >
    >
> MyMapping;