笔式三维建模系统的隐式映射机制

笔式三维建模系统支持用户基于纸笔隐喻自由勾画以表达三维模型,系统根据用户的交互意图完成相应的三维建模.针对笔式三维建模技术的交互特征,提出一种隐式映射机制.通过分析二维笔划以及交互的上下文,动态建立2个相互垂直的、虚拟的投影平面,从而将二维笔划信息平滑转换成三维空间信息.针对极限位置无法正常映射的情况,提出了一种坐标增量置换法来实现三维映射,不仅解决了极限位置的坐标映射,而且支持用户自由勾画更加复杂的三维模型.隐式映射机制将用户从繁琐、复杂的操作中解脱出来,集中精力关注创作灵感的表达.该方法已经在自主开发的笔式三维建模系统的原型系统PenSketch3D中得到验证,并取得了良好效果.

Implicit mapping mechanism in pen-based three-dimensional modeling system

The pen-based three-dimensional modeling system supports the user to sketch freely based on pen-paper metaphor so as to express three-dimensional models, and carries out corresponding three-dimensional modeling according to the user’s interaction intention. A kind of implicit mapping mechanism was proposed according to the characteristics of pen-based three-dimensional modeling technology. Two virtual projecting planes, which were vertical reciprocally, were constructed dynamically through analyzing the two-dimensional stroke and the interaction context so as to transform the two-dimensional stroke to three-dimensional spatial information smoothly. A method of coordinate increment replacement was proposed to dissolve the problems of mapping in ultimate positions. As a result, not only the problems of coordinate mapping from two-dimensional stroke tothree-dimensional spatial information in ultimate positions were settled, but also the user could sketch more freely to express much more complicated three-dimensional models. The user could be free from fussy and complicated operations by implicit mapping mechanism and concentrate on expressing his creative inspiration. It has been validated in a prototype system, PenSketch3D, with promising effect.