public void initWorld() { Vec2 gravity = new Vec2(0.0f, 9.8f); world = new World(gravity); // ground FixtureDef groundFixtureDef = new FixtureDef(); PolygonShape groundShape = new PolygonShape(); groundShape.setAsBox(20f, 0.1f); groundFixtureDef.shape = groundShape; groundFixtureDef.density = 25.0f; groundFixtureDef.filter = new Filter(); groundFixtureDef.filter.categoryBits = 0x0001; BodyDef groundBodyDef = new BodyDef(); groundBodyDef.position = new Vec2(0.0f, 3f); groundBodyDef.angle = 0.0f; groundBodyDef.type = BodyType.STATIC; groundBody = world.createBody(groundBodyDef); groundFixture = groundBody.createFixture(groundFixtureDef); }