How to connect two rigid parts while one would separate from the other halfway?

[Wong]

I need to model an object containing two connected rigid parts, A and B. A is usually used to collide with other bodies while B’s position is controlled by a controller designed by myself. When B is moving controlled by the controller, A would be following the B. And if I trigger an event from the controller, A would separate from B and be a freely falling body.

I tried to use “BilateralInteractionConstraint” component, but relative movement between A and B would happen when A is colliding with a rigid body. And the force feedback component could not compute the contact force at the same time.

I have thought some methods to solve this problem but I think they are cumbersome and clumsy. So I want to know if there’s any simple methods to model such an object.

[Hugo]

Hi Wong,

I used one single particle for your object.
Then I map a collision model (any mesh that you want) on this particle.
And I can still control the particle (here using a LinearMovementConstraint.

Here is the scene:

<Node name="root" gravity="0 0 0" dt="0.01"  >
    
    <CollisionPipeline verbose="0" draw="0" />
    <BruteForceDetection name="N2" />
    <MinProximityIntersection name="Proximity" alarmDistance="0.8" contactDistance="0.5" />
    <CollisionResponse name="Response" response="default" />

    <VisualStyle name="visualStyle1" displayFlags="showBehaviorModels  showCollisionModels" />

    <EulerImplicitSolver rayleighStiffness="0.01"/>
    <CGLinearSolver iterations="50" tolerance="1e-06" threshold="1e-06"/>

    <Node name="Sphere">
        <EulerImplicitSolver rayleighStiffness="0"/>
        <CGLinearSolver iterations="200" tolerance="1e-06" threshold="1e-06"/>
        <MechanicalObject template="Rigid" name="myParticle" position="-2 10 0    0 0 0 1" showObject="1" showObjectScale="0.5" />
        <UniformMass totalmass="1" />
        <ConstantForceField force="0 -1 0 0 0 0" />
        <!-- <Sphere name="Floor" listRadius="1" simulated="1" moving="1" contactStiffness="100" /> -->

        <Node name="object1_surf" activated="1" >
            <MeshObjLoader name="loader" filename="mesh/cube.obj" scale="10"/>
            <Mesh src="@loader" drawTriangles="0"/>
            <MechanicalObject name="MO_object1_surf" src="@loader" showObject="1"/>
            <Triangle />
            <Line />
            <Point />
            <RigidMapping input="@.." output="@MO_object1_surf"/>  

        </Node>

        <LinearMovementConstraint template="Rigid" keyTimes="0 1 5 10 12" movements="0 0 0   0 0 0
                                          0 0 0   0 0 0
                                          0 0 -20  0 0 0
                                          0 0 -20  0 0 60.3
                                          0 0 0   0 0 60.3" />
    </Node>

</Node>

Is this want you want to do?

Cheers,

Hugo

[Author]

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