Simulating the world.
WHAT A PHYSICS ENGINE PROVIDES
Rigid body simulation Collision detection and response Constraints and joints
Queries: rays, overlaps, sweeps
WHAT COLLISION DETECTION INVOLVES
Broad phase, eliminating distant pairs cheaply Narrow phase, computing exact contacts
WHAT COLLIDER SHAPES DIFFER IN
Cost, from cheapest primitives to expensive arbitrary meshes.
WHAT TO PREFER
Simple shapes, approximating the visual form.
WHY
Exact colliders are expensive and rarely necessary.
WHAT TUNNELLING IS
A fast object passing through a thin object between frames.
WHAT PREVENTS IT
Continuous collision detection, or thicker colliders, or smaller timesteps.
WHAT LAYERS PROVIDE
Control over what collides with what.
WHY THAT MATTERS
Most objects need not test against most others.
WHAT TRIGGERS ARE
Colliders detecting overlap without physical response.
WHAT THEY SUIT
Detection zones, pickups, and area effects.
WHAT TO KNOW ABOUT PHYSICS-DRIVEN GAMEPLAY
It is unpredictable, and difficult to tune precisely.
WHAT TO PREFER FOR PRECISE MOVEMENT
Direct control, with collision queries, rather than forces.
WHY
Physics-driven characters feel imprecise, which players notice immediately.
