3d的单向平台检测

https://www.youtube.com/watch?v=qwwjwb7XlUc

using UnityEngine;

[RequireComponent(typeof(BoxCollider))]
public class OneWayBoxCollider : MonoBehaviour
{
    /// <summary> The direction that the other object should be coming from for entry. </summary>
    [SerializeField] private Vector3 entryDirection = Vector3.up;
    /// <summary> Should the entry direction be used as a local direction? </summary>
    [SerializeField] private bool localDirection = false;
    /// <summary> How large should the trigger be in comparison to the original collider? </summary>
    [SerializeField] private Vector3 triggerScale = Vector3.one * 1.25f;
    /// <summary> The original collider. Will always be present thanks to the RequireComponent attribute. </summary>
    private new BoxCollider collider = null;
    /// <summary> The trigger that we add ourselves once the game starts up. </summary>
    private BoxCollider collisionCheckTrigger = null;

    /// <summary> The entry direction, calculated accordingly based on whether it is a local direction or not.
    /// This is pretty much what I've done in the video when copy-pasting the local direction check, but written as a property. </summary>
    public Vector3 Direction => localDirection ? transform.TransformDirection(entryDirection.normalized) : entryDirection.normalized;

    private void Awake()
    {
        collider = GetComponent<BoxCollider>();

        // Adding the BoxCollider and making sure that its sizes match the ones
        // of the OG collider.
        collisionCheckTrigger = gameObject.AddComponent<BoxCollider>();
        collisionCheckTrigger.size = new Vector3(
            collider.size.x * triggerScale.x,
            collider.size.y * triggerScale.y,
            collider.size.z * triggerScale.z
        );
        collisionCheckTrigger.center = collider.center;
        collisionCheckTrigger.isTrigger = true;
    }

    private void OnValidate()
    {
        // This bit of code exists only to prevent OnDrawGizmos from throwing
        // errors in the editor mode when it does not have reference to the
        // collider, if used.
        collider = GetComponent<BoxCollider>();
        collider.isTrigger = false;
    }

    private void OnTriggerStay(Collider other)
    {
        // Simulate a collision between our trigger and the intruder to check
        // the direction that the latter is coming from. The method returns true
        // if any collision has been detected.
        if (Physics.ComputePenetration(
            collisionCheckTrigger, transform.position, transform.rotation,
            other, other.transform.position, other.transform.rotation,
            out Vector3 collisionDirection, out float _))
        {
            float dot = Vector3.Dot(Direction, collisionDirection);

            // Opposite direction; passing not allowed.
            if (dot < 0)
            {
                // Making sure that the two object are NOT ignoring each other.
                Physics.IgnoreCollision(collider, other, false);
            }
            else
            {
                // Making the colliders ignore each other, and thus allow passage
                // from one way.
                Physics.IgnoreCollision(collider, other, true);
            }
        }
    }

    private void OnDrawGizmosSelected()
    {
        // Instead of directly using the transform.position, we're using the
        // collider center, converted into global position. The way I did it
        // in the video made it easier to write, but the on-screen drawing would
        // not take in consideration the actual offset of the collider.
        Gizmos.color = Color.red;
        Gizmos.DrawRay(transform.TransformPoint(collider.center), Direction * 2);

        Gizmos.color = Color.green;
        Gizmos.DrawRay(transform.TransformPoint(collider.center), -Direction * 2);
    }
}