1. A method of improving silhouette appearance in bump mapping comprising: a receiving step of receiving a triangle of a plurality of triangles; a checking vertex step of checking whether there is a vertex near silhouette in the triangle; a checking subdivision step of checking whether the triangle meets a predetermined criterion of subdivision if the result of the checking vertex step is “YES”; a subdividing step of subdividing the triangle if the result of the checking subdivision step is “YES”; a repeating step of repeating the receiving step, the checking vertex step, the checking subdivision step and the subdividing step until the triangle does not meet the predetermined criterion; a displacing step of displacing the vertex positions near silhouette along their normals according to the displacements obtained from displacement mapping if the result of the checking subdivision step is “NO”; and a bump mapping step of implementing bump mapping if the result of the checking vertex step is “NO”.