onCollisionEnter doesn't work without RIgidbody?

Question

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…

Airwoman

Answer 1

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.

Stemson

Strategy games are typically done using a grid, so you can check the grid position of each character in an array instead of using physics.

– Stemson

But I need two colliders to tell me when they collide. One is a rigidbody.

– Studnia

Yea but i have a problem, i have 2 gameObjects, both have Colliders and Rigidbody, but they don´t trigger the OnCollision event, why is it?

– Finfoot

Answer 2

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:

But for 3D.

Spunky

Answer 3

Triparted:

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

Kindling