دانلود رایگان مقاله بازنگری مدل داده تی اسپلاین و تبادل آنها با استفاده از STEP

Abstract

T-spline is a new approach to define freeform surfaces with relatively less control points than NURBS and is able to represent a model using a single surface without joining errors. Whereas, the complexity of T-spline data models leads numerous difficulties in its programming, which hinders the research and development of T-spline technologies. In addition, the data exchange of T-spline models still remains on a primitive level, and no standardized data format has been published so far. This article gives a reconsideration to the existing T-spline definitions, and proposes a set of redesigned data models which have much more understanding conveniences to both human and computer. Moreover, STEP-compliant data models are designed using the proposed T-spline models to standardize their data exchange between different CAx systems. The combination of T-spline with other product models in ISO 10303 makes it convenient to exchange the versatile resource data in a hybrid neutral file. A prototype system is developed for the validation purpose, which consists of a TSM-to-STEP convertor, a STEP parser and a T-spline kernel. Using the developed prototype system, one can automatically convert a Rhino system exported TSM file to a STEP file in the P21 format, which can be then parsed using the STEP reader and processed by the T-spline kernel. Some testing examples show that the proposed data models are much more efficient in processing and exchanging the T-spline data.

6. Discussion and conclusion

This paper reconsiders the drawbacks of the existing T-spline models, and proposes a set of new T-spline data models to obtain better data storing and operating efficiencies. The conventional T-mesh is decomposed into the parametric, topological, and Cartesian layers, respectively. The characteristics of the redesigned T-spline models are analyzed and reviewed. Using the proposed T-spline data structures, the STEP-compliant data models are presented for the standardized data exchange between different CAx systems in the future. A prototype system which consists of a TSM-to-STEP convertor, a STEP parser and a T-spline kernel, is proposed to implement the data models and realize the STEP-compliant data exchange. In order to verify the feasibility and efficiency, some T-spline examples have been tested and presented. The testing results prove that the new T-spline data models are much more friendly to both human and computer, hence have a great prospect for the future development of Tspline technologies. Although recent data models work well for the regular T-spline surfaces, other more generalized models have to be considered in the future. For example, unstructured T-splines with extraordinary vertices should be considered [28], T-NURCCS models will be supported for a manifold T-spline surface [1,29], volumetric T-spline will be defined for models with higher dimensions [30,31], and the research and development of newmodel based algorithms should be investigated and discussed.