onCollisionEnter doesn't work without RIgidbody?

[system]

Hi,
I am trying to check the collision between two colliders and OnCollisionEnter() doesn’t work unless one of the object is RigidBody. I can’t use Rigid Body for all the objects as it’s a way expensive…

Also tried with trigger and it doesn’t work without Rigidbody too… Anyone helps me…

[Eric5h5]

Correct. As shown in the docs, in order for anything to generate OnCollision events, one of the two objects involved must be a Rigidbody. There’s no way around that.

→ You don’t put a Rigidbody on everything, just the objects that move.

[wingsneon]

Well since none of these answers actually help solving the OP’s issue, I recommend anyone having this same problem to search about Physics.OverlapBox and/or Physics.OverlapSphere.

Just like this video shows:

MELEE COMBAT in Unity

But for 3D.

[andrew-lukasik]

@documentation

Collision generates collision detection messages

When a pair of colliders make contact, they generate collision detection
messages if the following are both true:

• There is at least one dynamic collider.
• The other collider is a static collider, a kinematic collider, or another dynamic collider.

The following table describes each combination of collider types. A “ ” indicates a combination that can generate collision detection and collision messages.

Collision detection occurs and messages are sent upon collision

	Static collider	Dynamic collider	Kinematic collider	Static trigger collider	Dynamic trigger collider	Kinematic trigger collider
Static collider
Dynamic collider
Kinematic collider
Static trigger collider
Dynamic trigger collider
Kinematic trigger collider

Source:

→ Unity - Manual: Interaction between collider types