[SOLVED] A Problem About How to Move A Fixed Rigid Object in C++ Project?

[wq57fan]

Hello,
I’m using SOFA in my simulation project.
I create a scene including some fixed rigid objects which use .obj files and collision models like TPOINTMODELS, TLINEMODELS, TTRIANGLEMODELS. And my tool could have collision with the objects using haptic device.
Now, I wish these rigid bodies could fall down with gravity so that my tool could move them. By referencing tutorials in MODELER, I tried using RIGIDMAPPING, but something goes wrong.
My question is: is there any other examples that could make a fixed rigid body falling down with gravity or make my haptic tool could move an object in C++?
Thank you!

[Hugo]

Hi wq57fan,

The Modeler is considered as deprecated. Moreover, be careful, you write that you want to make a fixed rigid body fall under gravity, this won’t obviously happen if your object is fixed !

To make a rigid body fall, you can write :

<Node name="RigidBody">
    <EulerImplicit />
    <CGLinearSolver iterations="50" tolerance="1e-09" threshold="1e-09" />
    <MeshGmshLoader name="meshLoader" filename="mesh/liver.msh" />
    <MechanicalObject template="Rigid" src="@ meshLoader" />
    <UniformMass totalMass="1" />
</Node>

About making your haptic tool move, I would advise you to have a look to the example scene associated to the Geomagic plugin : applications/plugins/Geomagic/scenes/Geomagic-FEMLiver.scn.

Let us know if this helps.

Hugo

[wq57fan]

Hi Hugo,
I tried your way, and it works in Modeler.

However, in my C++ project, there are two main problems existing:

1.The rigid body cannot detect the collision.

2.The rigid body cannot fall down with gravity.

Here is a part of my code:

	nodeFixed = chain->createChild("Fixed");

	sofa::component::odesolver::EulerImplicitSolver::SPtr solver = sofa::core::objectmodel::New<sofa::component::odesolver::EulerImplicitSolver>();    
	solver->setName("Euler Implicit");
	solver->f_rayleighStiffness.setValue(0.1);
	solver->f_rayleighMass.setValue(0.1);
	nodeFixed->addObject(solver);

	typedef sofa::component::linearsolver::CGLinearSolver< sofa::component::linearsolver::GraphScatteredMatrix, sofa::component::linearsolver::GraphScatteredVector> CGLinearSolverGraph;
	CGLinearSolverGraph::SPtr linear = sofa::core::objectmodel::New<CGLinearSolverGraph>();
	linear->setName("Conjugate Gradient"); //solver->setName("Conjugate Gradient");
	linear->f_maxIter.setValue(25); //iteration maxi for the CG
	linear->f_smallDenominatorThreshold.setValue(1e-05);
	linear->f_tolerance.setValue(1e-05);
	nodeFixed->addObject(linear);

	sofa::component::loader::MeshGmshLoader::SPtr loaderRigid = sofa::core::objectmodel::New<sofa::component::loader::MeshGmshLoader>();
	loaderRigid->setName("Msh Loader");
        loaderRigid->setFilename(sofa::helper::system::DataRepository.getFile("mesh/liver.msh"));
        loaderRigid->load();
        nodeFixed->addObject(loaderRigid);

	dofRigid = sofa::core::objectmodel::New<MechanicalObjectRigid3>(); 
	dofRigid->setName("Fixed Object");
        dofRigid->setSrc("@"+loaderRigid->getName(), loaderRigid.get());
	dofRigid->setTranslation(0,0,0);
	dofRigid->setRotation(0,0,0);
	nodeFixed->addObject(dofRigid);
	
	UniformMassRigid3::SPtr uniMassFixed = sofa::core::objectmodel::New<UniformMassRigid3>();
        uniMassFixed->setName("Uni Mass");
	uniMassFixed->setMass(1);
        uniMassFixed->setTotalMass(1); 
        nodeFixed->addObject(uniMassFixed);

	sofa::component::container::Node* nodeFixedVisual = nodeFixed->createChild("Visual");

	visualFixed = sofa::core::objectmodel::New<sofa::component::visualmodel::OglModel>();
	visualFixed->setName("visual");
	visualFixed->setFilename(sofa::helper::system::DataRepository.getFile(visualModelName1));
	visualFixed->setColor("gray");
	visualFixed->setTranslation(0,0,0);
	visualFixed->setRotation(0,0,0);
	nodeFixedVisual->addObject(visualFixed);

	visualModel[0] = visualFixed.get();

	const std::string refVisual3 = "@" + visualFixed->getName(); //output
	const std::string refDof3 = "@../" + dofRigid->getName();    //input
        RigidMappingRigid3d_to_Ext3f::SPtr mapping5 = sofa::core::objectmodel::New<RigidMappingRigid3d_to_Ext3f>();
        mapping5->setModels(dofRigid.get(), visualFixed.get());
	mapping5->setName("Mapping Visual");
	mapping5->setPathInputObject(refDof3);
	mapping5->setPathOutputObject(refVisual3);
        nodeFixedVisual->addObject(mapping5);

I don’t know that if it is because some of my parameters are wrong.

Thanks for your help.

[Hugo]

Hi wq57fan,

the C++ code you share does not include any MechanicalObject. Is that normal ?
To make your object fall under gravity, I see two issues: the MechanicalObject is missing and the gravity needs to be specified (you can set the gravity in the rootNode as a parameter).

For collision detection, you need to specify the collision topology. You can have a look at the scene examples/Components/collisionTriangleModel.scn which illustrate this well.

Let me know if this helps.

Hugo

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