1 files changed, 132 insertions, 0 deletions
diff --git a/Assets/Scripts/Core/Rope.cs b/Assets/Scripts/Core/Rope.cs
new file mode 100644
index 0000000..aff295a
--- /dev/null
+++ b/Assets/Scripts/Core/Rope.cs
@@ -0,0 +1,132 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+public class Rope : MonoBehaviour
+{
+    [SerializeField] protected int constraintIterations = 15;
+    [SerializeField] protected float gravityMultiplier = 1.0f;
+    [SerializeField] protected float lineWidth = 0.2f;
+    [SerializeField] protected float ropeSegmentLength = 0.1f;
+    [SerializeField] protected int segmentCount = 35;
+
+    protected LineRenderer lr;
+    protected DistanceJoint2D dj;
+    protected GameObject player;
+    protected List<RopeSegment> ropeSegments = new List<RopeSegment>();
+    protected Vector3[] ropePositions;
+    protected bool ropeCreated = false;
+
+    // Start is called before the first frame update
+    private void Start()
+    {
+        player = GameObject.FindGameObjectWithTag("Player");
+        dj = GetComponent<DistanceJoint2D>();
+        lr = GetComponent<LineRenderer>();
+        lr.startWidth = lineWidth;
+        lr.endWidth = lineWidth;
+        ropePositions = new Vector3[segmentCount];
+        lr.positionCount = segmentCount;
+        Vector2 ropeLoc = transform.position;
+
+        for (int i = 0; i < segmentCount; i++)
+        {
+            ropeSegments.Add(new RopeSegment(ropeLoc));
+            ropeLoc.y -= ropeSegmentLength;
+        }
+    }
+
+    // Update is called once per frame
+    private void Update()
+    {
+        if (!ropeCreated)
+        {
+            CreateRope();
+            ropeCreated = true;
+        }
+        RenderLine();
+        Simulate();
+    }
+
+    private void RenderLine()
+    {
+        for (int i = 0; i < ropePositions.Length; i++)
+        {
+            ropePositions[i] = ropeSegments[i].posNow;
+        }
+        lr.SetPositions(ropePositions);
+    }
+
+    private void CreateRope()
+    {
+        dj.connectedBody = player.GetComponent<Rigidbody2D>();
+        dj.maxDistanceOnly = true;
+        dj.distance = Vector2.Distance(player.transform.position, transform.position);
+    }
+
+    private void Simulate()
+    {
+        Vector2 gravityForce = new Vector2(0f, -gravityMultiplier);
+
+        for (int i = 0; i < ropeSegments.Count; i++)
+        {
+            RopeSegment segment = ropeSegments[i];
+            Vector2 velocity = segment.posNow - segment.posOld;
+            segment.posOld = segment.posNow;
+            segment.posNow += velocity;
+            segment.posNow += gravityForce * Time.deltaTime;
+            ropeSegments[i] = segment;
+        }
+
+        for (int i = 0; i < constraintIterations; i++)
+        {
+            ApplyContraint();
+        }
+    }
+
+    private void ApplyContraint()
+    {
+        RopeSegment endSegment1 = ropeSegments[0];
+        endSegment1.posNow = transform.position;
+        ropeSegments[0] = endSegment1;
+
+        RopeSegment endSegment2 = ropeSegments[ropeSegments.Count - 1];
+        endSegment2.posNow = player.transform.position;
+        ropeSegments[ropeSegments.Count - 1] = endSegment2;
+
+        for (int i = 0; i < ropeSegments.Count - 1; i++)
+        {
+            RopeSegment segment1 = ropeSegments[i];
+            RopeSegment segment2 = ropeSegments[i + 1];
+
+            float distance = (segment1.posNow - segment2.posNow).magnitude;
+            float error = distance - ropeSegmentLength;
+            Vector2 normalChange = (segment1.posNow - segment2.posNow).normalized;
+            Vector2 change = normalChange * error;
+
+            if (i != 0)
+            {
+                segment1.posNow -= change * 0.5f;
+                ropeSegments[i] = segment1;
+                segment2.posNow += change * 0.5f;
+                ropeSegments[i + 1] = segment2;
+            }
+            else
+            {
+                segment2.posNow += change;
+                ropeSegments[i + 1] = segment2;
+            }
+        }
+    }
+
+    public struct RopeSegment
+    {
+        public Vector2 posNow;
+        public Vector2 posOld;
+
+        public RopeSegment(Vector2 pos)
+        {
+            this.posNow = pos;
+            this.posOld = pos;
+        }
+    }
+}