效果展示：

 实现如下：

首先，直接上代码：

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

public class LineFourRender : MonoBehaviour
{
    public Transform StartNode;

    public Transform MidNode1;
    public Transform MidNode2;

    public Transform EndNode;
    public int vertexCount = 10;

    LineRenderer lineRen;

    private void Start()
    {
        lineRen = GetComponent<LineRenderer>();
    }
    private void Update()
    {

        List<Vector3> pointList = new List<Vector3>();


        for (float ratio = 0; ratio <= 1; ratio += 1.0f / vertexCount)
        {
            if (lineRen.useWorldSpace)
            {

                Vector3 tangentLineVertex1 = Vector3.Lerp(StartNode.position, MidNode1.position, ratio);
                Vector3 tangentLineVectex2 = Vector3.Lerp(MidNode1.position, MidNode2.position, ratio);
                Vector3 tangentLineVectex3 = Vector3.Lerp(MidNode2.position, EndNode.position, ratio);
                Vector3 bezierPoint1 = Vector3.Lerp(tangentLineVertex1, tangentLineVectex2, ratio);
                Vector3 bezierPoint2 = Vector3.Lerp(tangentLineVectex2, tangentLineVectex3, ratio);
                Vector3 bezierPoint = Vector3.Lerp(bezierPoint1, bezierPoint2, ratio);
                pointList.Add(bezierPoint);

            }
            else
            {
               Vector3 tangentLineVertex1 = Vector3.Lerp(StartNode.localPosition, MidNode1.localPosition, ratio);
                Vector3 tangentLineVectex2 = Vector3.Lerp(MidNode1.localPosition, MidNode2.localPosition, ratio);
                Vector3 tangentLineVectex3 = Vector3.Lerp(MidNode2.localPosition, EndNode.localPosition, ratio);
                Vector3 bezierPoint1 = Vector3.Lerp(tangentLineVertex1, tangentLineVectex2, ratio);
                Vector3 bezierPoint2 = Vector3.Lerp(tangentLineVectex2, tangentLineVectex3, ratio);
                Vector3 bezierPoint = Vector3.Lerp(bezierPoint1, bezierPoint2, ratio);
                pointList.Add(bezierPoint);

            }

        }
        if (lineRen.useWorldSpace)
        {
            pointList.Add(EndNode.position);
        }
        else
        {
            pointList.Add(EndNode.localPosition);
        }

        lineRen.positionCount = pointList.Count;
        lineRen.SetPositions(pointList.ToArray());
       // Draw(StartNode.position,EndNode.position,GetComponent<MeshRenderer>(),0.015).transform.SetParent(this.transform);

    }


}

接下来，把LineFourRender.cs拖拽上去：

注意：VertexCount参数决定了绳子的丝滑程度，该值越大，绳子越丝滑。

最后是对LineRenderer组件和绳子材质的调整：

附一张绳子贴图: