@article{zhu_lee_2005, title={A Visibility Sphere Marching algorithm of constructing polyhedral models for haptic sculpting and product prototyping}, volume={21}, ISSN={["1879-2537"]}, DOI={10.1016/j.rcim.2004.05.002}, abstractNote={This paper presents a Visibility Sphere Marching algorithm of constructing polyhedral models from Dexel volume models for haptic virtual sculpting. Dexel volume models are used as the in-process models representation during interactive modification in a haptic virtual sculpting system. The stock material represented in a Dexel volume model is sculpted into a designed model using a developed haptic sculpting system. The sculpted Dexel volume models are converted to polyhedral surface models in STL format by the proposed visibility sphere marching algorithm. The conversion turns out to be an interesting and challenging problem. The proposed visibility sphere marching algorithm consists of three sub-algorithms: (i) roof and floor covering, (ii) wall-building, and (iii) hole-filling algorithms. The polyhedral surface models converted from the Dexel volume models can then be input to and processed by available computer-aided manufacturing (CAM) or rapid prototyping systems. The presented technique can be used in virtual sculpting, CAD/CAM, numerically controlled machining verification and rapid prototyping.}, number={1}, journal={ROBOTICS AND COMPUTER-INTEGRATED MANUFACTURING}, author={Zhu, WH and Lee, YS}, year={2005}, month={Feb}, pages={19–36} }
 @article{ren_zhu_lee_2005, title={Material side tracing and curve refinement for pencil-cut machining of complex polyhedral models}, volume={37}, ISSN={["1879-2685"]}, DOI={10.1016/j.cad.2004.10.003}, abstractNote={In this paper, a new Material-Side-Tracing method and a pencil-cut curve refinement technique are proposed for 3-axis pencil-cut path generation. Pencil-cut machining has been used to remove remaining material at highly curved regions or corners after the finishing process. Procedures of evaluating and extracting valid pencil-cut points are developed by taking practical cases into account. With the strategy of using material-side information in the tracing process, smooth and clean pencil-cut curves can be generated even if the actual adjacent pencil-cut curves are very close. A technique of pencil-cut curve refinement is presented to overcome the limitation due to the discrete CL-net intervals, and the smooth pencil-cut paths are made complete at sharp corners. Computer implementation and practical examples are also presented in this paper. The proposed techniques can be used in the CAD/CAM systems to generate pencil-cut paths for machining complex polyhedral models.}, number={10}, journal={COMPUTER-AIDED DESIGN}, author={Ren, YF and Zhu, WH and Lee, YS}, year={2005}, month={Sep}, pages={1015–1026} }
 @article{zhu_lee_2004, title={Dexel-based force-torque rendering and volume updating for 5-DOF haptic product prototyping and virtual sculpting}, volume={55}, ISSN={["1872-6194"]}, DOI={10.1016/j.compind.2004.07.003}, abstractNote={This paper presents new techniques of Dexel-based force–torque rendering and volume-updating for haptic virtual sculpting of complex surfaces with a developed 5-DOF (degree of freedom) haptic interface. In the proposed methodology, 5-axis tool motion and analytical tool swept volume are formulated for updating the virtual stock material, which is represented with the Dexel volume model. Based on the tool motion analysis, a Dexel-based collision detection method and a force–torque feedback algorithm are proposed for virtual sculpting. A lab-built 5-DOF force–torque output haptic interface system is developed for the proposed haptic sculpting system. With the proposed methodology, a user can virtually sculpt a volume stock to get an intuitive design by using the haptic interface. From the haptic sculpting system, both the corresponding tool motion of the creative process and the sculpted model can be recorded and output. The output STL models of the haptic sculpting system can be processed for machining planning. Based on the proposed techniques, hardware and software implementation of the haptic sculpting system as well as the illustrative examples are also presented in this paper.}, number={2}, journal={COMPUTERS IN INDUSTRY}, author={Zhu, WH and Lee, YS}, year={2004}, month={Oct}, pages={125–145} }
 @article{zhu_lee_2004, title={Five-axis pencil-cut planning and virtual prototyping with 5-DOF haptic interface}, volume={36}, ISSN={["1879-2685"]}, DOI={10.1016/j.cad.2004.01.013}, abstractNote={In this paper, techniques of 5-axis pencil-cut machining planning with a 5-DOF (degree of freedom) output haptic interface are presented. Detailed techniques of haptic rendering and tool interference avoidance are discussed for haptic-aided 5-axis pencil-cut tool path generation. Five-axis tool path planning has attracted great attention in CAD/CAM and NC machining. For efficient machining of complex surfaces, pencil-cut uses relatively smaller tools to remove the remaining material at corners or highly curved regions that are inaccessible with larger tools. As a critical problem for 5-axis pencil-cut tool path planning, the tasks of tool orientation determination and tool collision avoidance are achieved with a developed 5-DOF haptic interface. A Two-phase rendering approach is proposed for haptic rendering and force-torque feedback calculation with haptic interface. A Dexel-based volume modeling method is developed for global tool interference avoidance with surrounding components in a 5-axis machining environment. Hardware and software implementation of the haptic pencil-cut system with practical examples are also presented in this paper. The presented technique can be used for CAD/CAM, 5-axis machining planning and virtual prototyping.}, number={13}, journal={COMPUTER-AIDED DESIGN}, author={Zhu, WH and Lee, YS}, year={2004}, month={Nov}, pages={1295–1307} }