floorGeometry.setMaterial(material);
floorGeometry.setLocalTranslation(0, -0.25f, 0);
// Plane plane = new Plane();
// plane.setOriginNormal(new Vector3f(0, 0.25f, 0), Vector3f.UNIT_Y);
// floorGeometry.addControl(new RigidBodyControl(new PlaneCollisionShape(plane), 0));
floorGeometry.addControl(new RigidBodyControl(0));
rootNode.attachChild(floorGeometry);
space.add(floorGeometry);
// movable spheres
for (int i = 0; i < 5; i++) {