کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
440255 | 690989 | 2012 | 9 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Adding draft angle to BB-spline and NURBS surfaces Adding draft angle to BB-spline and NURBS surfaces](/preview/png/440255.png)
BB-spline and NURBS surfaces are the most prevailing parametric surfaces in current CAD/CAM systems. Used for mould and die representations, they need sufficient draft angle in manufacturing processes. This paper tries to add draft angle to BB-spline and NURBS surfaces with minimum changes in their control nets and weights in the least square sense. An enhanced sufficient condition for BB-spline surfaces is introduced based on the convex combination, so as to improve the existing algorithm for adding draft angle to such surfaces. The draft angle distribution is visualized by a terrain, whose area under a certain level means that the corresponding part of the surface is too steep. Adding draft angle to this part can be expressed as a constraint on optimization. This idea is successfully applied to NURBS surfaces. Five examples demonstrate the effectiveness of the proposed methods.
► Enhance the draft angle conditions for bilinear interpolation & BB-spline surfaces.
► Optimization under the latter condition can add draft angle to BB-spline surfaces.
► Visualize the draft angle distribution all over a surface by a terrain.
► By comparing this terrain with a level, the ineligible regions become obvious.
► Propose a method for adding draft angle to NURBS surfaces.
Journal: Computer-Aided Design - Volume 44, Issue 7, July 2012, Pages 617–625