RBMuscle.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class RBMuscle : MonoBehaviour
{
    private const float TICK_EVERY_SECONDS = 1 / 25f; // 25 per second.

    [Header("Setup")]
    public bool _invert;
    [Space]
    public float _torqueForce;
    public float _angularDamping;
    public float _maxForce;
    public float _springForce;
    public float _springDaming;
    [Space]
    public Vector3 targetVel;

    [Header("Bind")]
    public Transform target;

    private ConfigurableJoint _join;
    private JointDrive _drive;
    private SoftJointLimitSpring _spring;
    private Quaternion _startingRotation;

    private float _secondsSinceLastTick = 0;

    private void Awake() {
        _join = GetComponent<ConfigurableJoint>();
    }

    void Start() {
        _invert = false;

        _torqueForce = 500f;
        _angularDamping = 0.0f;
        _maxForce = 500f;

        _springForce = 0f;
        _springDaming = 0f;

        targetVel = new Vector3(0f, 0f, 0f);

        _drive.positionSpring = _torqueForce;
        _drive.positionDamper = _angularDamping;
        _drive.maximumForce = _maxForce;

        _spring.spring = _springForce;
        _spring.damper = _springDaming;


        _join.slerpDrive = _drive;

        _join.linearLimitSpring = _spring;
        _join.rotationDriveMode = RotationDriveMode.Slerp;
        _join.projectionMode = JointProjectionMode.None;
        _join.targetAngularVelocity = targetVel;
        _join.enablePreprocessing = false;
        _join.configuredInWorldSpace = false;
        _join.swapBodies = true;

        _join.xMotion = ConfigurableJointMotion.Locked;
        _join.yMotion = ConfigurableJointMotion.Locked;
        _join.zMotion = ConfigurableJointMotion.Locked;

        _join.angularXMotion = ConfigurableJointMotion.Free;
        _join.angularYMotion = ConfigurableJointMotion.Free;
        _join.angularZMotion = ConfigurableJointMotion.Free;

        _startingRotation = Quaternion.Inverse(target.localRotation);
    }

    private void Update() {
        _secondsSinceLastTick += Time.deltaTime;

        if (_secondsSinceLastTick < TICK_EVERY_SECONDS) return;

        Tick();
    }

    private void Tick() {
        _secondsSinceLastTick = 0;

        if (_invert)
            _join.targetRotation = Quaternion.Inverse(target.localRotation * _startingRotation);
        else
            _join.targetRotation = target.localRotation * _startingRotation;
    }
}