Continuous collision (CCD)

A body moving fast enough can skip right over a thin obstacle in a single step — it’s on one side before the step, the other side after, and never overlaps. That’s tunneling. Continuous collision detection (CCD) fixes it by sweeping the body’s motion.

Both spheres below are fired at the same speed. The red one uses the default discrete motion quality and punches through the wall; the green one uses linearCast and is stopped.

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Red: discrete (tunnels). Green: linearCast (stops at the wall).

How it works

Set motionQuality per body:

// Default: fast + cheap, but can tunnel through thin geometry.
world.createBody({ type: "dynamic", shape: Shape.sphere(0.22), motionQuality: "discrete" });

// Sweeps the motion so thin walls are never skipped.
world.createBody({ type: "dynamic", shape: Shape.sphere(0.22), motionQuality: "linearCast" });

CCD costs more, so reserve linearCast for things that actually move fast — projectiles, fast vehicles — and leave everything else on discrete.

Related

• Bodies & motion — the full list of body options.