Why won't collisions work unless a rigid body is specified

Unity Engine
1

I am working on a 2D side scroller where we are creating platforms on one side of the screen and deleting them on the other side. Right now the platforms are 3D cube objects with a BoxCollider2D and there is another cube on the edge of the screen with a BoxCollider2D that handles destroying objects. The platforms have a basic script assigned to it that adjusts the position each update.

The issue is when these platforms hit the BoxCollider2D that handles object deletion the collision callback never gets hit. What I noticed is once I added a RigidBody2D to the platforms was when I was receiving the callbacks. So my question is why does an object need a RigidBody in order for a collision to be detected? Why can’t I just do a BoxCollider2D to BoxCollider2D collision test?

I am using Unity 5.3.2f1.

Thanks for any input

2

Because the physics system assumes that colliders without a rigidbody are static and therefore should never collide with other static objects. This is an optimisation so that all static colliders around your level aren’t all checked against each other.

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