Unity 2D One Way Platform

Lately I've been using a lot of Unity's new 2D features, and one thing that has been driving me nuts is the Platform Effector 2D, specifically it's One Way function.

 The One Way Effector doesn't ignore horizontal collisions, and only ignores vertical collisions while the colliding object is travelling upwards. When an object's upward momentum is not great enough to clear the platform the Effector kicks in and violently pushes the object away, or, if the object has multiple colliders (like the Standard Assets Platformer Character) it may get stuck half-way through. This may be the very literal description of a one-way collider, but in practice it's not very useful.

I made numerous attempts to create a better One Way Platform and in the end I settled on the simplest solution. My method utilizes a Trigger Collider on the character(s), and a Tag on the One Way Platforms.

Note: Rather than using tags, an alternative method would instead assign One Way Platforms to a specific layer.  The code would then compare the layer instead of the tag.  The benefit to this would be to easily allow certain objects (like projectiles or flying characters) to completely ignore One Way Platforms via Physics2DSettings > LayerCollisionMatrix.

using UnityEngine; using System.Collections.Generic; [RequireComponent (typeof (Collider2D))] public class OneWayController : MonoBehaviour { public String m_OneWayTag = "OneWayPlatform"; //Tag to use for one way platforms List <Collider2D> m_ActorColliders; //List of colliders on this character void Awake () { //Cache refrences to this character's colliders in a list m_ActorColliders = new List<Collider2D>(); Collider2D[] colliders = GetComponents<Collider2D>(); for (int i = 0; i < colliders.Length; i++) { //Exclude the one way trigger from the collider list if (!colliders[i].isTrigger) m_ActorColliders.Add(colliders[i]); } } void OnTriggerEnter2D (Collider2D other) { //When a platform with the one way tag enters the trigger                 //ignore collisions between it and this character if (other.Tag == m_OneWayTag) { for (int i = 0; i < m_ActorColliders.Count; i++) { Physics2D.IgnoreCollision(other, m_ActorColliders[i], true); } } } void OnTriggerExit2D (Collider2D other) { //When the platform exits the trigger re-enable collisions if (other.Tag == m_OneWayTag) { for (int i = 0; i < m_ActorColliders.Count; i++) { Physics2D.IgnoreCollision(other, m_ActorColliders[i], false); } } } }

The result is One Way Platforms that allow characters to pass through them on three sides without interruption.  The only drawback is that raycasts could be blocked by the trigger colliders on characters, if that is an issue you can go to Edit > Project Settings > Physics 2D > and uncheck "Raycasts Hit Triggers".