The Billboard sample illustrates the billboarding technique. Rather than rendering complex 3D models (such as a high-polygon tree model), billboarding renders a 2D image of the model and rotates it to always face the eyepoint. This techniqu

向3d场景中添加树木。十字交叉树和始终面向观察者！-Adding trees to the 3d scene. Cross tree and always facing the observer!