createWorld method
Makes a world. Throws a Physics3DUnsupportedError saying why when unavailableReason is not null.
Implementation
@override
PhysicsWorld3D createWorld(PhysicsWorldSettings3D settings) {
final reason = unavailableReason;
if (reason != null) throw Physics3DUnsupportedError(reason);
final world = FakePhysicsWorld3D(
settings,
collisions: collisions,
owner: this,
);
worlds.add(world);
return world;
}