this.rootNode = rootNode;
this.physicsSpace = physicsSpace;
this.assetManager = assetManager;
this.sky = new Sky(assetManager, DEFAULT_SKY_COLOR, DEFAULT_HORIZON_COLOR, DEFAULT_HORIZON_SCALE, DEFAULT_GROUND_COLOR);
this.ground = new Ground(assetManager, 1000.0f, DEFAULT_GROUND_COLOR);
addWorldObject(this.sky);
addWorldObject(this.ground);
ambientLight = new AmbientLight();