Physics-first play

Balancing physics for play

Wheel physics was a balancing challenge. Purely realistic physics without differentials and suspension does not automatically create a good player experience. Even with gears, joints, electric connections and logic parts, the goal was a moderate level of complexity that remained fun to play.

UGC added another constraint: player-built vehicles cannot be expected to use the usual four symmetric wheel layout assumed by conventional vehicle systems such as wheel colliders.

Custom wheel logic

We developed custom wheel logic to provide better grip and suspension behaviour without requiring separate suspension parts. Each wheel controlled itself and used configurable joints to change its physical characteristics during a ride.

The wheels sensed their surroundings through raycasts organised around their own needs. Most of those raycasts were batched, so the system could stay responsive without becoming a performance problem.

Custom wheel physics in Hello Engineer · Silent loop.

Designing target behaviour

For balancing, we built testing levels and wrote rules describing the intended behaviour of each vehicle part. At one point in a test level, a vehicle should feel bouncy and a little hard to control as it drives over obstacles such as rocks; at another, it should take a turn smoothly at maximum speed while staying on the ground.

Other scenarios defined when a vehicle should lose grip, jump from a cliff, or slide into a drag state depending on the surface, torque and angle. These targets turned a vague feeling of “good physics” into cases the team could test and tune.

Surface-aware particles

We also developed a smart particle system. Each effect could contain up to three particles at once, emitted and blended according to velocity, direction, surface, power and other conditions.

Surface-aware particle effects in Hello Engineer · Silent loop.