Vehicle physics
The simulation that makes cars, bikes and trucks accelerate, lean and lose grip — from arcade drift to millimetre-exact racing sim.
Two schools dominate. The cheap one uses raycast vehicles: the wheels are rays, not bodies. The expensive one simulates the tyre for real — slip ratio and slip angle feed a tyre model such as Pacejka's "magic formula" to compute grip. On top sit suspension as a spring-damper, a drivetrain with engine torque and gears, and weight transfer that pitches the nose down under braking. The gulf between Mario Kart and iRacing lives largely here. Engines like Bullet, PhysX and Unity's WheelCollider supply the building blocks; the hard part is tuning them so the car feels right rather than merely being correct.