unity 3d：刚体.AddForce（forceDirection.normalized *力）将对象移离父级和关节

Question

So, this seems to be a strange one (to me). I'm relatively new to Unity, so I'm sure this is me misunderstanding something.

I'm working on a VSEPR tutorial module in unity. VSEPR is the model by which electrons repel each other and form the shape (geometry) of atoms.

I'm simulating this by making (in this case) 4 rods (cylinder primitives) and using rigidbody.AddForce to apply an equal force against all of them. This works beautifully, as long as the force is equal. In the following image you'll see the rods are beautifully equi-distant at 109.47 degrees (actually you can "see" their attached objects, two lone pairs and two electron bonds...the rods are obscured in the atom shell.)

(BTW the atom's shell is just a sphere primitive - painted all pretty.)

HOWEVER, in the real world, the lone pairs actually exert SLIGHTLY more force...so when I add this additional force to the model...instead of just pushing the other electron rods a little farther away, it pushes the ENTIRE 4-bond structure outside the atom's shell.

THE REASON THIS SEEMS ODD IS...two things.

1. All the rods are children of the shell...so I thought that made them somewhat immobile compared to the shell (Ie if they moved, the shell would move with them...which would be fine).

2. I have a ConfiguableJoint holding the rods to the center of the atoms shell ( 0,0,0). The x/y/z-motion is set to fixed. I thought this should keep the rods fairly immutably attached to the 0,0,0 center of the shell...but I guess not.

POINTS OF INTEREST:

• The rods only push on each other, by a script attached to one rod adding force to an adjacent rod. they do not AddForce to the atom shell or anything else.

CODE:

void RepulseLike() {

    if (control.disableRepulsionForce) { return; }  // No force when dragging

    //////////////////// DETERMINE IF FORCE APPLIED //////////////////////////////
    // Scroll through each Collider that this.BondStick bumps
    foreach (Collider found in Physics.OverlapSphere(transform.position, (1f))) {

        // Don't repel self
        if (found == this.collider) { continue; }

        // Check for charged particle
        if (found.gameObject.tag.IndexOf("Charge") < 0) { continue; }// No match "charge", not a charged particle   


        /////////////// APPLY FORCE ///////////////
        // F = k(q1*q2/r^2)
        // where 
        // k = Culombs constant which in this instance is represented by repulseChargeFactor
        // r = distance
        // q1 and q2 are the signed magnitudes of the charges, in this case -1 for electrons and +1 for protons

        // Swap from local to global variable for other methods
        other = found;

        /////////////////////////////////
        // Calculate pushPoints for SingleBonds
        forceDirection = (other.transform.position - transform.position) * magnetism; //magnetism = 1

        // F = k(q1*q2/distance^2), q1*q2 ia always one in this scenario. k is arbitrary in this scenario
        force = control.repulseChargeFactor * (1 / (Mathf.Pow(distance, 2)));

        found.rigidbody.AddForce(forceDirection.normalized * force);// * Time.fixedDeltaTime);

    }//Foreach Collider

}//RepulseLike Method

Answer 1

您可能希望使用球体来表示电子，因此要在其上施加力并根据该球体重新定向（旋转）棒。

Answer 2

I think I found my own answer...unless someone has suggestions for a better way to handle this.

I simply reduced the mass of the electron rods, and increased the mass of the sphere. I'm not sure if this is the "best practices" solution or a kluge...so input still welcomed :-)