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);
        }
    }
}

Yes, this works on all platforms.

…

On Mon, Jun 10, 2019, 18:41 Michael Levine ***@***.***> wrote: Will this work on iOS and Android mobile devices? thanks — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://gist.github.com/ae6ebc115d767da9a5a1e1f70dee27e5?email_source=notifications&email_token=AACTOUVS5RL7MBGJLQZ7WWDPZZ74HA5CNFSM4HWVEFU2YY3PNVWWK3TUL52HS4DFVNDWS43UINXW23LFNZ2KUY3PNVWWK3TUL5UWJTQAFTNY2#gistcomment-2939789>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AACTOURKUKCGJAJLWM3TNILPZZ74HANCNFSM4HWVEFUQ> .

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 ?