jelito/Assets/jelycho/Code/Ropes/PhysicsRope.cs

using System.Collections.Generic;
using System.Runtime.CompilerServices;
using UnityEngine;
using UnityEngine.Assertions;
using Logger = RebootKit.Engine.Foundation.Logger;

namespace RebootReality.jelycho.Ropes {
    public class PhysicsRope : MonoBehaviour {
        static readonly Logger s_Logger = new Logger(nameof(PhysicsRope));

        [Header("Core Settings")]
        [SerializeField] ConfigurableJoint m_JointPrefab;
        [SerializeField] float m_MaxSegmentDistance = 0.5f;

        [Header("Initialization")]
        [SerializeField] bool m_ConfigureOnStart = true;
        [SerializeField] float m_InitialLength = 2f;
        
        readonly List<RopeSegment> m_Segments = new List<RopeSegment>(16);
        float m_RopeLength;
        
        public Rigidbody HeadRigidobody {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get {
                return m_Segments.Count == 0 ? null : m_Segments[0].rigidbody;
            }
        }

        public Rigidbody TailRigidobody {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get {
                return m_Segments.Count == 0 ? null : m_Segments[m_Segments.Count - 1].rigidbody;
            }
        }

        void Awake() {
            if (m_ConfigureOnStart) {
                Configure(m_InitialLength);
            }
        }

        public void Configure(float length) {
            Clear();

            m_RopeLength = length;
            
            Vector3 startPosition = transform.position;
            Vector3 endPosition = startPosition - Vector3.up * m_RopeLength;

            for (float len = 0.0f; len < m_RopeLength; len += m_MaxSegmentDistance) {
                float t = len / m_RopeLength;
                Vector3 segmentPosition = Vector3.Lerp(startPosition, endPosition, t);
                
                ConfigurableJoint joint = Instantiate(m_JointPrefab,
                                                      segmentPosition,
                                                      Quaternion.identity);
                Transform segmentTransform = joint.transform;

                if (m_Segments.Count == 0) {
                    Destroy(joint);
                    joint = null;
                } else {
                    joint.connectedBody = m_Segments[m_Segments.Count - 1].rigidbody;
                }
                
                Rigidbody jointRigidbody = segmentTransform.GetComponent<Rigidbody>();
                Assert.IsNotNull(jointRigidbody, "Joint Prefab must have a Rigidbody component.");

                m_Segments.Add(new RopeSegment {
                    joint = joint,
                    rigidbody = jointRigidbody,
                    transform = segmentTransform
                });
            }
        }

        void Clear() {
            m_Segments.Clear();
        }

        struct RopeSegment {
            public Transform transform;
            public ConfigurableJoint joint;
            public Rigidbody rigidbody;
        }
    }
}