TOOL PATH PLANNING FOR MACHINING FREE-FORM SURFACES

This paper is about new iso-parametric tool path planning for machining trimmed free-form surfaces. The trimmed surface has been re-parameterized by two different parameterization techniques, namely, the partial differential equation method and the newly developed boundary interpolation method. The efficiency of the scheme has been measured in terms of path length and computational time needed for machining some typical surfaces. Conventionally, the forward-step is calculated by approximating the cutting curve with the osculating circle. The actual tolerance of the forward-step may go beyond the prescribed limit due to the circular arc approximation. In this study, the actual cutting curve has been considered to keep the tolerance in the forward-step below the prescribed value. The new algorithm has been tested on some typical surfaces and the results show a significant improvement in the surface profile in terms of tolerance of the forward-step

A GPU-based architeture for supporting 3D interactions

Orientador: Wu Shin-TingTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de ComputaçãoResumo: Tendo como hipótese de que o controle preciso do movimento de um cursor constitui uma das técnicas elementares para as tarefas de manipulação direta 3D, esta tese propõe uma arquitetura de suporte a controles configuráveis dos movimentos de cursores em relação a modelos deformados em hardware gráfico. De forma integrada ao fluxo programável de visualização, a arquitetura calcula atributos de geometria diferencial discreta dos modelos processados, codificando tais atributos em pixels de buffers de renderização não visíveis. Mostramos, através de estudos de casos, que o uso desses atributos é suficiente para estabelecer uma correspondência entre o espaço discreto do modelo renderizado na tela e o espaço contínuo do modelo submetido ao fluxo de visualização. Isto permite que os cursores sejam posicionados de forma consistente com aquilo que o usuário está visualizando, proporcionando uma interação mais acurada. Testes de desempenho e robustez são conduzidos para validar a arquitetura. Uma biblioteca de funções que encapsula a arquitetura é apresentada, juntamente com exemplos de tarefas de manipulação direta 3D implementadas através delaAbstract: Based on the hypothesis that the precise control of the motion of a cursor constitutes one of the elementary techniques for 3D direct manipulation tools, this thesis proposes an architecture for supporting a configurable control of the motion of cursors with respect to models deformed on graphics hardware. Integrated with the actual programmable rendering pipeline, the architecture computes discrete differential geometric attributes of the processed models and encodes such attributes in pixels of off-screen render buffers. We show, through case studies, that these attributes are sufficient to establish a correspondence between the discrete space of the model rendered on the screen and the continuous space of the model submitted to the rendering pipeline. As a result, the cursors can be positioned consistently with what the user is actually viewing, thus providing a more accurate interaction. Efficiency and reliability tests are conducted to validate the architecture. A library of functions that encapsulates the architecture and examples of 3D direct manipulation tasks implemented with it are also presented.DoutoradoEngenharia de ComputaçãoDoutor em Engenharia Elétric