摘要
自从快速成型系统出现以来，一直沿用STL文件进行切片数据处理。但是STL文件错误较多，精度较低，数据量也较大。目前快速成型设备的性能已经有了长足的进步，曲面加工，微小件的加工要求越来越高。于是研究者们尝试对STL文件数据进行后处理，或提出基于CAD系统二次开发的直接切片。而本文采取了一种不同的方式，彻底摒弃了STL文件，也不采用CAD平台二次开发，而是直接实观基于NURBS曲面的直接切片求交算法。尝试以这种方式，克服STL文件的缺陷。同时，与基于CAD系统二次开发的直接切片相比，不依赖CAD平台，不涉及版权问题，所以更利于直接切片技术的商品化。
研究了适用于快速成型的曲面／平面求交追踪算法的实现。对追踪算法中所存在的初始追踪点搜索，追踪方向迷失，步长的确定，边界的处理等问题进行了深入探索，提出了相应的解决办法。并设计了B样条曲线／曲面求值的快速算法，曲面求极值点的单纯形算法，曲线／平面求交算法，曲面求交的迭代算法，点到曲面的投影算法等一系列辅助直接切片的算法。采用object pascal语言编写了直接切片软件DirectSlice，完成了对算法的验证和测试。
还研究了数据交换，交线结果的组织等技术，使得数据能够顺利的输入输出。开发了基于OpenGL的图形显示组件，用于三维模型及运算结果的真实感显示。
直接切片研究尝试了一条新的数据处理的思路，不需要STL文件和CAD平台。这个思路虽然计算复杂，但是可提高精度，可靠性，及处理速度，并降低数据传输量。
Since RP system was invented, STL file has been widely used as data exchange file. But STL file has lots of disadvantages, such as error, limited precision, and large data volume. Recently, RP device's performance has been highly improved. Requirements of surface machining, micro-workpiece machining become higher and higher, so some researchers try to pre-process STL files for improving its precision. Others design their slice processing software on CAD platform. But this paper doesn't flow such ideas. Neither STL files nor CAD platforms are used. An algorithm for Surface/plane intersection that Direct-slice processing based on is designed and implemented in this paper. Direct-slice processing in this paper can get rid of STL files' disadvantages, and work without CAD platform. So it has own copyright, and is more competitive in business application.
surface/plane intersection is the key technology of direct slice processing. Tracing intersection method for direct-slicing processing is implemented in this paper. Many problems of tracing intersection method have been researched, such as original tracing points searching, lost tracing orientation, tracing step calculating, boundarys processing. Related solutions of those problems are put forward. Furthermore, A serial of assistant algorithms are developed for direct-slicing too. Testing and validating of algorithms are completed, via a test software Direct Slice, which is designed in Object Pascal computer language.
Data exchanging and the interpolation of intersection points are researched too. Because 3D Model viewing is necessary for graphics software, OpenGL Model display component is also designed and implemented.
This paper is try to find a new method for RP data processing, without STL files and CAD platform. The Direct-slice processing in this paper is a complex algorithm, but stability, higher precision, small data volume are available.
引文
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