Abstract: Vertices of triangle meshes are searched for updating its z-value after each cutting pass. Construct a rectangle box a little bit wider than the one that just encloses all neighboring triangles that share the common vertex which needs refreshing, and redraw all triangles entirely enclosed and partially covered by the bounding box. The partially covered triangles are accessed through detecting one of their vertices by scanning all pixels located on the x-direction boundary of box along y-direction upward and downward. In comparison with Vericut and Mastercam, the proposed approach gives comparable performance both in speed and quality of simulation.