Abstract: A method for efficient calculation of the movement of a vertex in a three-dimensional topography simulator. The method is particularly well suited for calculating vertex movement for cases in which an etch/deposition rate depends on the angle between the surface normal and the vertical direction. A workpiece is represented as a collection of material solids. Each of the material solids has a boundary model representation, which include vertices, edges and faces. The method of the present invention generally includes the steps of: identifying a first plane, a second plane and a third plane that approximate all the planes that are adjacent to a vertex point to be moved; determining a first observation vector; creating a set of advanced virtual planes; identifying a second observation vector; determining the furthest intersection point of one of the planes in the set of advanced planes and the second observation vector; and moving the vertex to the point identified in the prior step.