1·TreeBillboard: terrain engine billboarded trees.
地形引擎中的广告牌树。
2·Objects that are only billboarded on one or more axes will face the camera on those axes, but may rotate around other axes.
而有些只在一个或两个轴向遵循这个原则的物体则只会在相应的轴向上面对镜头，并且可以以其他轴向旋转。