Witness (Delaunay) Graphs

Proximity graphs are used in several areas in which a neighborliness relationship for input data sets is a useful tool in their analysis, and have also received substantial attention from the graph drawing community, as they are a natural way of implicitly representing graphs. However, as a tool for graph representation, proximity graphs have some limitations that may be overcome with suitable generalizations. We introduce a generalization, witness graphs, that encompasses both the goal of more power and flexibility for graph drawing issues and a wider spectrum for neighborhood analysis. We study in detail two concrete examples, both related to Delaunay graphs, and consider as well some problems on stabbing geometric objects and point set discrimination, that can be naturally described in terms of witness graphs.Comment: 27 pages. JCCGG 200

Adaptive Planar Point Location

We present a self-adjusting point location structure for convex subdivisions. Let n be the number of vertices in a convex subdivision S. Our structure for S uses O(n) space and processes any online query sequence sigma in O(n + OPT) time, where OPT is the minimum time required by any linear decision tree for answering point location queries in S to process sigma. The O(n + OPT) time bound includes the preprocessing time. Our result is a two-dimensional analog of the static optimality property of splay trees. For connected subdivisions, we achieve a processing time of O(|sigma| log log n + n + OPT)

The Parallel 3D Convex-Hull Problem Revisited - Revision 1

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / CCR-89-0641

An Optimal Algorithm for Determining the Separation of Two Nonintersecting Simple Polygons

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / N00014-90-J-127

Ambiente de desenvolvimento de manufatura virtual

The demand for foreign equipments in teaching institutions is well-know. To properly train an engineer, a lot of hours in several equipments are required. This is a problem if the equipments are expensive. The problem increases if manufacturing automation and control are focus. The number of equipments needed to simulate real industrial problems is enormous and even if considering the unlikable possibility that founds are not the problem, the physical space would be. To overcome this problem, the present work introduces a robotic and manufacturing framework. Based on the virtual reality present on games this framewo rk enables one to generate any desirable rigid-body scenario raging from manufacturing process to robot, manipulators, pneumatic engines and others. The graphics quality as well its physical behaviors enables an operator to live a realistic immersion in the virtual environment.A demanda por equipamentos importados em instituições de ensino é um fato conhecido. Este problema se agrava quando a área envolvida é o controle e automação da manufatura, onde os equipamentos utilizados possuem um alto custo. Para que um treinamento de controle destes equipamentos seja tido como satisfatório é necessário que um aluno, além do estudo teórico, faça diversas simulações e observe as respostas dos diversos equipamentos e das formas de programação e ajuste. Para contornar esta situação este projeto propõe a montagem de um ambiente virtual para treinamento em robótica e manufatura integrada. Utilizando técnicas semelhantes às dos tão conhecidos jogos em realidade virtual será construído um ambiente onde será possível a visualização, montagem e programação de quaisquer processos de manufatura, como robôs, mesas pneumáticas, esteiras, etc. A qualidade gráfica da simulação, bem como seu comportamento físico coerente e sua flexibilidade permitem uma imersão realística no ambiente virtual

A haptic stencil for manufacturing applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 86-90).The haptic stencil consists of a 5 DOF haptic device and an anti-collision algorithm that acts as a geometric stencil and can be used for a variety of applications ranging from training to rapid prototyping and manufacturing. Online manipulation of a three-axis desktop milling machine was established using this setup. This work describes the algorithm design used to achieve the required performance and stencil-like behavior with specific reference to machining applications. Some of the primary aspects of this design include the collision detection, collision remediation and control methodologies employed. The parameters on which these methodologies depended and how they were developed are the focus of this work. Collision detection is the core of any haptic interaction as it determines whether or not contact has been established between the virtual objects and therefore is essential in deciding the appropriate haptic feedback. In the case of the haptic stencil, the collision detection algorithm would have to identify whether or not contact occurs between the haptic probe-controlled tool object and the stationary part object. Collision remediation provides the stencil-like behavior by enforcing geometric constraints on the regions/surfaces by preventing penetration by the tool object. The results from the collision detection and collision remediation modules are used to control the desktop milling machine which cuts out a copy of the part object used in the haptic simulation from a given stock according to the motions specified on the haptic probe by the operator. Speed control is necessary in order to ensure that motions from the human operator are not lost due to the different communication speeds between the various modules of this setup.(cont.) Speed control also helps in providing as 'real-time' a machining experience as possible for a given part and stock combination.by Kirti Ramesh Mansukhani.S.M

Efficient collision detection for real-time simulated environments

Thesis (M.S.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 1994.Includes bibliographical references (leaves 64-68).by Paul Jay Dworkin.M.S