How do I tell if an object is currently colliding with another object?

Question

I know this sounds simple, but I can't figure out how to tell if a GameObject is currently colliding with another object in Unity. I've looked online, but can't find any tutorials or answers that work.

Also, what's the difference between a Collision and a Collider?

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My dilemma:

I have a third person controller set up and I'm trying to give it the ability to wall jump. There is already an isGrounded function, so I just need to test if I'm hitting anything other the the floor, and it will wall jump backwards.

I've already tried: if (this.OnCollisionEnter){ ... }

if (Collider.OnCollisionEnter){ ... } Wrong use.

I now tried:

function OnCollisionStay(){
   Debug.Log("Collision");
}

I checked my logs and my console, but still can't find anything.

Answer 1

1. The function MonoBehavior.OnCollisionStay() (link) is called every frame for every collider that is touching another collider there are also OnCollisionEnter() (link) and OnCollisionExit() (link) for similar behavior at the start and end of contact. If you want to do something while your object is being collided with, put that function in a script on that object and put your code in there.

2. A Collider is the object that does the colliding. The Collision is the event/data that tells you about the collision. Some explanation can be found here and other places in the Unity docs.

Answer 2

Based on Unity script reference, Collision is a class representing all the information about a collision. It's a parameter passed to Collider.OnCollisionEnter, Collider.OnCollisionStay and Collider.OnCollisionExit events. Collider on the other hand is everything that has a physical representation.

So if you want to know whether an object is colliding with any other object in the game, you have to define a collider for both of them, and implement OnCollisionEnter event for the object you are interested in.