Unity Physics (Rigidbody / PhysX)

Make objects move, collide, and detect each other with Unity 6's built-in 3D physics (PhysX). Get the FixedUpdate discipline, trigger-vs-collision rules, and collision layers right. Targets Unity 6 (6000.0 LTS).

Unity 6 rename: Rigidbody.velocity is now Rigidbody.linearVelocity (the old name is deprecated). Code copied from older tutorials will warn or fail to compile.

When to use

• Use when giving an object physical motion (forces, velocity, gravity), responding to collisions or triggers, setting up collision layers/masks, raycasting for ground checks or line-of-sight, or connecting bodies with joints.
• Use when scenes/prefabs contain Rigidbody + Collider components.

When not to use: 2D physics (Rigidbody2D, Collider2D) is a separate API — adapt the concepts but the types differ. Cross-engine feel tuning (timestep, jitter, tunnelling) → physics-tuning. Reading input that drives movement → unity-input-system.