Kinematic platform

Kinematic bodies are moved by you, not by forces — but they still push dynamic bodies correctly. The trick is moveKinematic, which sets a velocity so the body arrives at the target next step, rather than teleporting. That carried velocity is what lets a platform ferry its cargo and bulldoze loose boxes.

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How it works

const platform = world.createBody({
  type: "kinematic",
  shape: Shape.box({ halfExtents: [1.4, 0.15, 1.4] }),
  position: [-3, 0.5, 0],
  layer: "moving",
});

let time = 0;
function tick(dt) {
  time += dt;
  const x = Math.sin(time * 0.7) * 3; // where the platform should be next
  platform.moveKinematic([x, 0.5, 0], [0, 0, 0, 1], dt);
  world.step(dt);
}

moveKinematic vs setTransform

setTransform teleports — a resting box would be left behind and dynamic bodies wouldn’t be pushed. moveKinematic derives the velocity from the move, so contacts resolve properly. Use it for anything that should carry or shove other bodies.

Related

• Bodies & motion — static, kinematic, and dynamic bodies.