What is a Collider?

Learn collision shapes like Box Collider and Sphere Collider.

What is a Collider?

Collider components are invisible collision volumes defining a GameObject's physical boundaries. Without a Collider, other objects pass right through it like a ghost.

// Adding a box collision boundary
BoxCollider box = gameObject.AddComponent<BoxCollider>();
box.size = new Vector3(1f, 2f, 1f);

The visual 3D model and physical collision volume are decoupled; MeshRenderer draws the visuals, while Collider governs collisions.

Primitive and Complex Collider types

The most common primitive types are BoxCollider, SphereCollider, and CapsuleCollider. These primitives are mathematically very fast to compute.

// Setting SphereCollider radius
SphereCollider sphere = GetComponent<SphereCollider>();
sphere.radius = 0.5f;

A MeshCollider wrapping every polygon vertex is much more costly, so it is generally reserved for static environment assets.

Exercise Print Collider profile

Assign "SphereCollider" to colliderType and "0.5" to radius. Print Collider: SphereCollider | Radius: 0.5 to the console.

Show example solution

using System;

class Program
{
    static void Main()
    {
        string colliderType = "SphereCollider";
        string radius = "0.5";
        Console.WriteLine("Collider: " + colliderType + " | Radius: " + radius);
    }
}

Test yourself

Which component is most appropriate for defining collision bounds of a spherical object?
- CanvasScaler
- NavMeshObstacleOnly
- SphereCollider
- AudioReverbZone
Show answer

SphereCollider — SphereCollider provides the most optimized collision check for spherical geometry using center and radius.

Attach SphereCollider component

SphereCollider sphere = gameObject.AddComponent<____>();

Show answer

SphereCollider sphere = gameObject.AddComponent<SphereCollider>();

Collider types

BoxCollider

Box-shaped collision volume
SphereCollider

Sphere volume defined by radius
CapsuleCollider

Capsule collision for character bodies
MeshCollider

Collision following model surface

Next lesson: Applying force with AddForce

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