It answers a simple question: what part of this object can touch, block, overlap, or be queried?
Why Colliders Exist
Artwork is not a reliable collision shape.
A model might be visually complex. A sprite might have transparent pixels, soft edges, or a pose that changes during animation. Physics needs a simpler shape it can test quickly and predictably.
That is what a Collider provides.
Common Collider Shapes
Common collider shapes include:
- boxes for platforms, walls, crates, rooms, and simple characters
- spheres for balls, pickups, sensors, and radial effects
- capsules for upright characters and rounded actors
- cylinders and cones for pillars, posts, wheels, and tapered volumes
- triangle meshes for static 3D level geometry such as floors, ramps, and terrain
- 2D boxes and circles for flat 2D gameplay spaces
Choose the shape that matches the gameplay need, not necessarily the exact artwork.
Collider and Rigidbody
A Collider defines shape.
A Rigidbody defines physics movement.
They often work together.
For example, a moving 3D ball might have a Rigidbody3D and a SphereCollider3D. The Rigidbody handles motion, while the collider defines the ball's physical shape.
In a 2D game, the same idea uses Rigidbody2D with 2D collider components.
Static level geometry may only need colliders if it does not move.
Solid Colliders and Triggers
Some colliders are solid.
Solid colliders can block or physically interact with other colliders.
Some colliders are triggers.
Triggers detect overlap without acting like a wall. They are useful for pickup zones, damage zones, checkpoints, area entrances, and invisible sensors.
Physics Materials
Collider shape answers what can touch. A physics material answers how that contact should feel.
In 3D, assign a Physics Material 3D asset to BoxCollider3D, SphereCollider3D, CapsuleCollider3D, CylinderCollider3D, or MeshCollider3D when a surface needs custom friction or bounce. For example, an icy ramp can use low friction, while a rubber ball can use high bounciness.
In 2D, use Physics Material 2D assets for the equivalent collider workflow.