Tsuyoshi Saitoh

Face-based data structure and its application to robust geometric modeling

Robust manipulation of a geometric model, that is free from computational errors, is one of the difficult prohIems in geometric modeling, and its algorithm is not established especially for the boundary representation. This paper proposes a new face-based data structure and a robust algorithm for processing polyhedra represented in the data structure. The face-based structure is introduced for representing solids without redundancy, represent ing designer’s intentions and constraints on faces, and administrating computational errors smoothly. The construction of the algorithms is based on a concept: the geometric model should be generated to be able to manufacture a product. According to this concept, the following three principles are employed. Fundamental data are coefllcients of a plane equation and coordinate values of vertices which include computational errors are treated as secondary. This is natural for the purpose of manufacturing products, because designer’s intentions are represented with faces and objects of machining are faces. Incidence tests among geometrical elements such aa vertices, edges and faces are performed by the minimum height of a tetrahedron made by four faces. This makes the algorithm independent from a sequence of faces for the calculations of solids. A local topological structure, where many faces intersect at near a point and ambiguities of the topology remain, is determined according to a global feature of a shape represented by a property of edges, that is concave or convex. 111this paper, the incidence check is explained geometrically. Algorithms for Boolean set operations are presented along with classification of incident patterns, and some examples executed by them are shown. Permission to copy without fee all or part of this material is granted provided that the copies are not made or dktributed for direct commercial advantage, the ACM copyright notice and the title of the publication and Its date appear, and notice is given that copyin is by permission of the Association of Computing Machinery. o cop otherwise, or to republish, requires y ! a fee and/or specl ICpermission, Solid Modeling ’95, Salt Lake City, Utah USA

A Study on Motion Visualization System Using Motion Capture Data

In this paper, we describe a development of the motion visualization system which make us understand intuitively a series of action of an actor by coordinates information obtained from motion capture system (MC system). The MC system we use is wireless magnetic type and has 11 sensors each which give us position and angle data. To visualize the motion of limbs, we transform momentary position and/or angle data from corresponding sensor into color lines and place the line in a row every moment. As a result, the motion of a sensor is shown as an image like a color belt on display. The idea of this method is based on principle of slit camera. Once the image is generated, we can get some characteristics of motion by image processing techniques without original sensor data. Some examples of the image and extracted features from the image will be shown.Accompanying the progress of medical technology, all kinds of treatment and therapy are being practiced in healthcare industry. It is expected that the regional difference in terms of the quality of healthcare in the area of surgery could be reduced through the remote operations with the help of a robot-based surgery system. Such a remote surgery approach, however, is not yet practical, because it solely relies on the visual perception with no input for the haptic perception. Since it is a lot faster for a human being to sense through touching than by watching especially when he is manipulating an object, sensing through touching is considered essential to the success of remote surgery. In this research, a system that is able to sense through a force sensor is developed. The system simulates the process of intracytoplasmic sperm injection (ICSI). PHANToM, a force sensing system, is employed for collecting the information for the haptic perception. With this force sensing system, it is possible to have force input in 6 degrees of freedom and force output in 3 degrees of freedom. OpenGL is used for the 3D graphics rendering in the visual information processing system. By synchronizing the information for both the visual and haptic perception, a virtual reality system that reacts to both the visual and force interactions has been developed. The simulation results reported in this paper proved that using the information collected through the force sensing system makes a significant difference in the medical treatment.

Interpolating Clothoidal Spline Curve by Computer Algebra System.

広く普及してきた汎用の数式処理システムを導入することによって, 形状設計分野で有用性が認められているクロソイドスプライン補間曲線をより一般的に手軽に導く方法を示すことができた.与点通過の拘束条件に種々の境界条件式を実行時にデータとして与えてこれらの非線形の条件式を連立してニュートン法で直接解くことができた.数式処理機能に合わせた注意深い定式化によってプログラムを極めて簡潔に記述することができた.これはまた数式処理機能のこの分野での有用性の一端を例証するものであると考える.一方, クロソイドスプライン補間曲線は比較的制約が強いこともわかったので, 今後, 本研究の考え方を拡張して1スパンが複数個のクロソイド弧からなる曲線, 曲率が弧長の2～3次関数となる曲線あるいはそれらの複合曲線といったより柔軟性のある曲線を考えてゆきたい.そして, 曲率プロファイルの制御による補間曲線の一般的な形状制御法を考えてゆきたい.