Rope Physics

DistanceJoint3D.cs

using UnityEngine;

public class DistanceJoint3D : MonoBehaviour {

    public Transform ConnectedRigidbody;
    public bool DetermineDistanceOnStart = true;
    public float Distance;
    public float Spring = 0.1f;
    public float Damper = 5f;

    protected Rigidbody Rigidbody;

    void Awake()
    {
        Rigidbody = GetComponent<Rigidbody>();
    }

    void Start()
    {
        if (DetermineDistanceOnStart && ConnectedRigidbody != null)
            Distance = Vector3.Distance(Rigidbody.position, ConnectedRigidbody.position);
    }

    void FixedUpdate()
    {

        var connection = Rigidbody.position - ConnectedRigidbody.position;
        var distanceDiscrepancy = Distance - connection.magnitude;

        Rigidbody.position += distanceDiscrepancy * connection.normalized;

        var velocityTarget = connection + (Rigidbody.velocity + Physics.gravity * Spring);
        var projectOnConnection = Vector3.Project(velocityTarget, connection);
        Rigidbody.velocity = (velocityTarget - projectOnConnection) / (1 + Damper * Time.fixedDeltaTime);


    }
}

FrictionJoint3D.cs

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

public class FrictionJoint3D : MonoBehaviour {

    [Range(0,1)]
    public float Friction;

    protected Rigidbody Rigidbody;
    
    void Awake()
    {
        Rigidbody = GetComponent<Rigidbody>();
    }

    void FixedUpdate()
    {
        Rigidbody.velocity = Rigidbody.velocity * (1 - Friction);
        Rigidbody.angularVelocity = Rigidbody.angularVelocity * (1 - Friction);
    }



}

RopeRoot.cs

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

public class RopeRoot : MonoBehaviour {

    public float RigidbodyMass = 1f;
    public float ColliderRadius = 0.1f;
    public float JointSpring = 0.1f;
    public float JointDamper = 5f;
    public Vector3 RotationOffset;
    public Vector3 PositionOffset;

    protected List<Transform> CopySource;
    protected List<Transform> CopyDestination;
    protected static GameObject RigidBodyContainer;

    void Awake()
    {
        if(RigidBodyContainer == null)
            RigidBodyContainer = new GameObject("RopeRigidbodyContainer");

        CopySource = new List<Transform>();
        CopyDestination = new List<Transform>();

        //add children
        AddChildren(transform);
    }

    private void AddChildren(Transform parent)
    {
        for (int i = 0; i < parent.childCount; i++)
        {
            var child = parent.GetChild(i);
            var representative = new GameObject(child.gameObject.name);
            representative.transform.parent = RigidBodyContainer.transform;
            //rigidbody
            var childRigidbody = representative.gameObject.AddComponent<Rigidbody>();
            childRigidbody.useGravity = true;
            childRigidbody.isKinematic = false;
            childRigidbody.freezeRotation = true;
            childRigidbody.mass = RigidbodyMass;

            //collider
            var collider = representative.gameObject.AddComponent<SphereCollider>();
            collider.center = Vector3.zero;
            collider.radius = ColliderRadius;

            //DistanceJoint
            var joint = representative.gameObject.AddComponent<DistanceJoint3D>();
            joint.ConnectedRigidbody = parent;
            joint.DetermineDistanceOnStart = true;
            joint.Spring = JointSpring;
            joint.Damper = JointDamper;
            joint.DetermineDistanceOnStart = false;
            joint.Distance = Vector3.Distance(parent.position, child.position);

            //add copy source
            CopySource.Add(representative.transform);
            CopyDestination.Add(child);

            AddChildren(child);
        }
    }

    public void Update()
    {
        for (int i = 0; i < CopySource.Count; i++)
        {
            CopyDestination[i].position = CopySource[i].position + PositionOffset;
            CopyDestination[i].rotation = CopySource[i].rotation * Quaternion.Euler(RotationOffset);
        }
    }
}

Thank you! One other question: Can the ropes collide with the environment and with each other? And can they be attached to rigid bodies? thanks

Can you help please? The rope is in 4 segments with 4 bones plus a tail bone. Script is on the first bone. No errors showing.
Thank you.

How is the "RotationOffset" being calculated? The rope appears as a zig zag without segments being rotated. If the segments are very small the zig zag may be hard to see.

Hello. Where should the three rows be placed ?

please make another video again and this time give us the 3d model too so we dont need to make it so size issues will not be there and please this time how to use the scripts where to attach them and how to modify if it startst to fly tell these too