Colliders & Triggers

Colliders & Triggers

Collider Components

A Collider defines the physical shape of a GameObject for collision detection.

• Box Collider: A rectangular box shape.
• Sphere Collider: A spherical boundary.
• Capsule Collider: A capsule shape.
• Mesh Collider: Uses the 3D model geometry itself for absolute accuracy.

Physical Collisions

When two solid objects bump into each other, physical contact occurs. Use:

• OnCollisionEnter(Collision collision): Runs when contact is first made.
• OnCollisionStay(Collision collision): Runs repeatedly while contact remains.
• OnCollisionExit(Collision collision): Runs when contact ends.

Triggers (Non-physical boundaries)

If you check the Is Trigger box on a Collider component, the collider no longer acts as a solid object. Objects pass straight through it. For trigger interactions, use:

• OnTriggerEnter(Collider other): Runs when an object enters the zone.
• OnTriggerStay(Collider other): Runs while an object stays in the zone.
• OnTriggerExit(Collider other): Runs when an object leaves the zone.

Rule of thumb

For physics collision/trigger events to fire:

• Both objects must have Collider components.
• At least one of the objects must have an active Rigidbody component.

TL;DR

• Physical collisions block movement and trigger OnCollision... methods.
• Triggers let objects pass through, firing OnTrigger... methods.
• One of the colliding objects must have a Rigidbody for events to fire.