Local mesh decimation for view-independent three-axis NC milling 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 work-piece, thus enabling dynamic viewing transformations without reconstruction of the entire data structure. However, the polygon rendering technique still has difficulty in realising real-time simulation owing 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, a new mesh decimation algorithm is proposed for a 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 work-piece 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 realising the polygon rendering-based NC simulation in real-time on computers equipped with general graphics cards.