To realize the illusion of bumpy of geometric surface, traditional bump mapping changes the normals of geometric surface instead of changing the geogetric attributes of body surface.

• 传统的凹凸纹理映射技术并没有真正改变物体表面的几何属性,而是通过纹理来改变物体表面的法向量,从而实现物体表面具有粗糙感的假象。