Local Mesh Decimation for Real-time Three-axis Nc Milling Graphical Simulation

The view dependency of typical z-buffer-based NC simulation methods is overcome by a polygon rendering technique that generates polygons to represent the workpiece, thus enabling dynamic viewing transformations without reconstruction of the entire data structure. However, the polygon rendering technique still has difficulty in realizing real-time simulation due to the limited performance of current graphics devices. Therefore, it is necessary to develop a mesh decimation method that enables rapid rendering without loss of display quality. To meet this requirement, in this paper, we propose a new mesh decimation algorithm for the workpiece which is represented by the z-map structure and whose shape is dynamically changed by the tool. In this algorithm, the z-map data for the workpiece are divided into several regions, and a triangular mesh is constructed for each region. Then, if the tool cuts any region, its mesh is regenerated and decimated again. Since the range of mesh decimation is confined to a few regions, the reduced triangles for rapid rendering can be obtained in a short time. This local mesh decimation method may contribute toward realizing the polygon rendering-based NC simulation in real time on computers equipped with general graphics cards.