[SOLVED] Creating attractive forces

[mikelitu]

Hello everyone,

I am trying to build an attractive path over a mesh surface to travel with my haptic device. For this purpose I want to generate a line connecting different control points from the surface and create an attractive force over it. I am new to SOFA and I do not know how to extract all the needed information for this purpose. How can I extract some indices from a mesh surface and generate a line over them? How can I generate an attractive force (similar to gravity), over this line? Thank you for your attention.

Mikel

[Hugo]

Hey @mikelitu

For this, you can use the component RepulsiveSpringForceField. It is an old and dirty class but working. It will create an attractive (if stiffness<0) or repulsive (if stiffness>0) force between points of two different MechanicalObjects.

Here is an example :

<?xml version="1.0"?>
<Node name="root" dt="0.001" gravity="0 0 0">
    <VisualStyle displayFlags="showBehaviorModels showForceFields" />
    <DefaultPipeline verbose="0" draw="0" />
    <BruteForceDetection name="N2" />
    <MinProximityIntersection name="Proximity" alarmDistance="0.8" contactDistance="0.5" />
    <DefaultContactManager name="Response" response="default" />

    <Node name="Floor">
        <RegularGridTopology nx="30" ny="1" nz="30" xmin="7" xmax="-7" ymin="-4" ymax="-4" zmin="-7" zmax="7"/>
        <MechanicalObject template="Vec3d"  name="FloorMO" showObject="1"/>
    </Node>

    <Node name="cubeFEM">
        <EulerImplicitSolver name="cg_odesolver" printLog="false"  />
        <CGLinearSolver iterations="25" name="linear solver" tolerance="1.0e-9" threshold="1.0e-9" />
        <MechanicalObject template="Vec3d" name="cubeMO"/>
        <UniformMass vertexMass="0.25" />
        <RegularGridTopology nx="5" ny="5" nz="5" xmin="-3.5" xmax="3.5" ymin="-3.5" ymax="3.5" zmin="-3.5" zmax="3.5" />
        <TetrahedronFEMForceField name="FEM" youngModulus="25" poissonRatio="0.3" computeGlobalMatrix="false" updateStiffnessMatrix="false" method="large" />
        <RepulsiveSpringForceField template="Vec3d" name="RSFF" stiffness="-200" damping="100" length="1" object1="@cubeMO" object2="@../Floor" indices1="0 4 100 104 52" indices2="232 217 682 667 435"/>

        <Node name="Visu">
            <MeshObjLoader name='myLoader' filename='mesh/smCube125.obj'/>  
            <OglModel name="Visual" src="@myLoader" color="red" />
            <SubsetMapping input="@.." output="@Visual" />
        </Node>
    </Node>

</Node>

you can use it to adapt it to your case.
Best

Hugo

[mikelitu]

Hello Hugo,

Thank you for your answer I will try this fuction and will adapt it to my case.

Best,
Mikel

[Hugo]

Hey @mikelitu

Any update regarding the use of the RepulsiveSpringForceField?
Best wishes,

Hugo

[mikelitu]

Hi @Hugo,

I tried this function but it was not what I was looking for in this case. I am trying a new approach with the SlidingConstraint function. I openned a new topic with an issue I have while using it here #16976.

Best,
Mikel

[Author]

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