[SOLVED] Translating mechanical objects (not working c++)

[OEA]

Hello, I would like some help. I am trying to apply translations to a mechanical model that was loaded by a .scn file, I fetch the object and confirm i have a valid point but the applyScale() function does nothing, as you can see from the code i confirm i have the correct object and i print the scale after modification which returns(1,1,1)

sofa::simulation::Node::SPtr groot = sofa::simulation::getSimulation()->load("./scene.scn");
	// print out scene tree, confirm mechnical model existsance
groot->printComponents();
		groot->getTreeNode(std::string("TT"))->printComponents();
		sofa::simulation::Node* lol = groot->getTreeNode(std::string("TT"));
//get pointer to mechnical model and print its name to confirm validity
		sofa::core::behavior::BaseMechanicalState* liver = &lol->mechanicalState[0];
		cout << liver->getName();
	cout << liver;
	//if(liver)
	
	liver->applyScale(0.7, 9.7, 0.7);
// prints scale, the output is (1,1,1) not above scale
	cout << liver->getScale();
	sofa::simulation::tree::getSimulation()->init(groot.get());

My scene graph file is Tetra2TriangleTopologicalMapping_NoInitialTriangle_option.scn

[OEA]

I have also tried transformation visitor with no sucess

[Hugo]

Hi @omarehaly,

If you access the MechanicalObject of your scene, you should be able to do (before the init() ):

your_mechanicalObj->setTranslation(dx, dy, dz);

This should work. HTH,

Hugo

[OEA]

Thank you, that’s what I am doing in the pasted coded. I examined the api and it says that MechanicalState only stores information about the physical object and modifying its values will not affect the calculations. I guess that explained why my code is not working.

How can I easily and dynamically alter the position of an object, this object will not need to be constrained by physics.

SOFA is well documented but the sheer number of data types and templates makes it hard to find the right data type and function to use.

[mslib]

How can I easily and dynamically alter the position of an object, this object will not need to be constrained by physics.

I have done something similar by loading my object twice. MObj_1 has translation applied to it, and MObj_2 is attached to MObj_1 with springs or fixed attachments in certain parts. MObj_2 will react dynamically to MObj_1’s translation.

[Anna]

Hi,

Regarding the source, applyTranslation and applyRotation seem to apply your delta directly to the positions so that should work in your case.

[Hugo]

Another way, would be to use Python for interacting during runtime. This is the most straightforward approach on my point of view.

[Weng]

Have you tried the MechanicalStateController in SofaUserInteraction Project? The mechanical state could be modified in the following steps:

(1) get the MechanicalState
using core::behavior::MechanicalState;
mState = dynamic_cast<MechanicalState<DataTypes> *> (this->getContext()->getMechanicalState());

(2) get the WriteAccessor of position
helper::WriteAccessor<Data<VecCoord> > x = *this->mState->write(core::VecCoordId::position());
helper::WriteAccessor<Data<VecCoord> > xfree = *this->mState->write(core::VecCoordId::freePosition());

(3) modify the center or orientation
x[i].getCenter() = position;
xfree[i].getOrientation() = orientation;

Best Regards,
Weng Bin

[BEK]

Thank you Weng Bin.
I also has similar problems to translate object in C++, your comment was very helpful.

For me, I usually access using tags from collision models.
LIKE this, <PointModel tags="Tool"/> this code is in the child node.

and tried to move this collision model to certain positions using MechanicalObject.
But it doesn’t works.. (looks like back to the initial position)
Should I access parent node to move object?

[Hugo]

Hi Bek,

If you use a mapping, mapping the collision (slave) onto the mechanical model (master), and you change the position of the collision model, the mapping will overwrite the position since the master representation is the mechanical model.
Does this make sense?

Are the meshes used for the collision and the mechanics the same mesh?
Could you send us more details about your scene and the code written to move the collision model?

Best,

Hugo

[BEK]

sorry for late reply.
Thank you Hugo.
As you said, because of mapping, I should move mechanical model instead of collision model.
I solve that problems using BaseMechanicalState.
Thank you for your help!
Best,

BEK

[Author]

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