Piercing Arrow in Unity

ArrowTipTrigger.cs

using UnityEngine;

public class ArrowTipTrigger : MonoBehaviour
{
    void OnTriggerEnter(Collider other)
    {
        SendMessageUpwards("OnArrowTipTriggerEnter", other, SendMessageOptions.RequireReceiver);
    }
}

PiercingArrow.cs

using UnityEngine;

public class PiercingArrow : MonoBehaviour
{
    public enum ArrowState 
    {
        Flying,
        Penetrating,    // After body hits, before creating joint
        Embedded
    }
    
    // Configuration
    public float pierceAngleTolerance = 30f;
    public float minImpactVelocity = 5f;
    public float maxRelativeVelocityForJoint = 0.5f;
    public float penetrationDampingFactor = 5f;
    public float rigidbodyVelDampingOnPeneteration = .75f;
    public Collider[] tipColliders;
    public CapsuleCollider bodyCollider;
    public Collider arrowTipTriggerCol;
    public bool debug = false;

    // Runtime state
    public ArrowState currentState = ArrowState.Flying;
    private Vector3 penetrationDirection;
    
    // Cached components
    private Rigidbody arrowRigidbody;
    private ArticulationBody targetArticulationBody;

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

    private void HandlePenetrationSlowdown()
    {
        // Project current velocity onto penetration direction
        Vector3 velocityAlongPenetration = Vector3.Project(arrowRigidbody.linearVelocity, penetrationDirection);
        Vector3 velocityPerpendicular = arrowRigidbody.linearVelocity - velocityAlongPenetration;

        // Apply damping only to the penetration component
        Vector3 dampedVelocityAlongPenetration = velocityAlongPenetration / (1f + Time.fixedDeltaTime * penetrationDampingFactor);
    
        // Calculate and apply impulse based on the change in velocity
        Vector3 velocityChange = dampedVelocityAlongPenetration - velocityAlongPenetration;
        Vector3 impulse = arrowRigidbody.mass * velocityChange;
        targetArticulationBody.AddForceAtPosition(impulse, arrowTipTriggerCol.transform.position, ForceMode.Impulse);

        // Recombine velocities and apply
        arrowRigidbody.linearVelocity = velocityAlongPenetration + velocityPerpendicular;
    }

    void OnArrowTipTriggerEnter(Collider other) // Called via SendMessageUpwards on arrow tip trigger collider
    {
        if (debug)
            Debug.Log($"OnArrowTipTriggerEnter: {other.gameObject.name}");
        if (currentState != ArrowState.Flying)
            return;
        
        if // IS NOT AN OBJECT YOU WANT TO PENETRATE
            return;
        
        Vector3 relativeVelocity = arrowRigidbody.linearVelocity - other.attachedArticulationBody.linearVelocity;
        if (relativeVelocity.magnitude < minImpactVelocity)
        {
            if (debug)
                Debug.Log($"Penetration rejected: velocity {relativeVelocity.magnitude} < {minImpactVelocity}");
            return;
        }

        float impactAngle = _getPiercingAngle(arrowTipTriggerCol, other);
        if (impactAngle > pierceAngleTolerance) 
        {
            if (debug)
                Debug.Log($"Penetration rejected: angle {impactAngle} > {pierceAngleTolerance}");
            return;
        }

        if (debug)
            Debug.Log($"Penetration accepted! collision.articulationBody: {other.attachedArticulationBody}");

        targetArticulationBody = other.attachedArticulationBody;
        
        DisableCollisionsWithTarget(other);
        currentState = ArrowState.Penetrating;
        penetrationDirection = transform.forward;
        arrowRigidbody.linearVelocity *= (1 - rigidbodyVelDampingOnPeneteration);
        Vector3 impulse = arrowRigidbody.mass * arrowRigidbody.linearVelocity;
        targetArticulationBody.AddForceAtPosition(impulse, arrowTipTriggerCol.transform.position, ForceMode.Impulse);
    }
    
    private float _getPiercingAngle(Collider triggerCollider, Collider otherCollider)
    {
        if (Physics.ComputePenetration(
                triggerCollider, triggerCollider.transform.position, triggerCollider.transform.rotation,
                otherCollider, otherCollider.transform.position, otherCollider.transform.rotation,
                out Vector3 direction, out float distance))
        {
            // direction is pointing from triggerCollider to otherCollider
            // We want angle between arrow's forward and the negative of this direction
            return Vector3.Angle(transform.forward, -direction);
        }
        return 180f; // No penetration detected
    }
  
    void OnTriggerStay(Collider col)
    {
        if (currentState == ArrowState.Penetrating && col.attachedArticulationBody != null && col.attachedArticulationBody == targetArticulationBody)
        {
            HandlePenetrationSlowdown();
            float relativeVelocity = (targetArticulationBody.linearVelocity - arrowRigidbody.linearVelocity).magnitude;
            if (debug)
                Debug.Log($"Penetrating - RelativeVelocity: {relativeVelocity}, Target: {maxRelativeVelocityForJoint}");
        
            if (relativeVelocity <= maxRelativeVelocityForJoint)
            {
                if (debug)
                    Debug.Log("Velocity check passed, creating joint");
                CreateFixedJoint();
                currentState = ArrowState.Embedded;
            }
        }
    }

    void OnTriggerExit(Collider col)
    {
        if (col.attachedArticulationBody == targetArticulationBody)
        {
            currentState = ArrowState.Flying;
        }
    }

    private void DisableCollisionsWithTarget(Collider targetCollider)
    {
        foreach (Collider tipCollider in tipColliders)
        {
            Physics.IgnoreCollision(tipCollider, targetCollider);
        }
        Physics.IgnoreCollision(bodyCollider, targetCollider);
    }

    private void CreateFixedJoint()
    {
        FixedJoint joint = gameObject.AddComponent<FixedJoint>();
        joint.connectedArticulationBody = targetArticulationBody;
        joint.breakForce = Mathf.Infinity;
        joint.breakTorque = Mathf.Infinity;
    }
}