Undo facilities for the extended z-buffer in NC machining simulation
We present here an improvement of the extended z-buffer. This object representation is well adapted to the Numerical Control (NC) machining simulation, with many thousand tool positions, as practiced in the workshops. However, it does not keep in memory the history of the machining of the workpiece. We propose an algorithm that consists in setting-up undo facilities by using new functionalities called traces. The latter contain all the information necessary to display and to model again the workpiece at any specific moment of the simulation. To implement the traces efficiently, we also introduce Interval Treaps (Treap: tree and heap), a new data structure based on the interval binary search trees (BSTs). The experimental evaluations will show that an interactive and user-friendly animation can be set up. Finally, to adapt the simulation to the performances expected by the users, we propose a new method, which identifies the machining strategy used to generate the toolpaths, the first essential step to predict the memory requirements and the speed of simulation. (C) 2003 Elsevier B.V. All rights reserved.
extended z-buffer interval treap data structures geometric modeling nc milling simulation