Remuestreo estructurado de contornos de huecos en superficies 3d de objetos de forma libre utilizando bresenham

La etapa de integración dentro del proceso de reconstrucción tridimensional de objetos de forma libre, requiere de la descripción, análisis y corrección de huecos en superficies 3D. Ciertas evaluaciones cuantitativas en este tema implican contar con conjuntos de datos espaciados de forma regular o contenidos en estructuras que garanticen dicha propiedad, por ejemplo voxels, octrees o mallas estructuradas. Lograr lo anterior requiere un proceso de re-muestreo de los puntos que conforman el contorno del hueco en la superficie 3D. En este trabajo se describe un método para obtener conjuntos estructurados de puntos, a partir de los datos de contornos de huecos en objetos de forma libre. El método inicia con el ajuste de una curva NURBS al conjunto inicial de puntos con el fin de asegurar la suavidad del contorno, de lo cual se obtiene un conjunto de puntos ajustados. Finalmente se utiliza el algoritmo de discretización de Bresenham para obtener el conjunto de puntos estructurados. Los resultados obtenidos muestran que el método desarrollado asegura que el conjunto final de puntos estructurados preserven la forma del contorno original con altos niveles de detalle

An analysis of surface area estimates of binary volumes under three tilings

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 77-79).by Erik G. Miller.M.S

A knowledge-based approach for the extraction of machining features from solid models

Computer understanding of machining features such as holes and pockets is essential for bridging the communication gap between Computer Aided Design and Computer Aided Manufacture. This thesis describes a prototype machining feature extraction system that is implemented by integrating the VAX-OPS5 rule-based artificial intelligence environment with the PADL-2 solid modeller. Specification of original stock and finished part geometry within the solid modeller is followed by determination of the nominal surface boundary of the corresponding cavity volume model by means of Boolean subtraction and boundary evaluation. The boundary model of the cavity volume is managed by using winged-edge and frame-based data structures. Machining features are extracted using two methods : (1) automatic feature recognition, and (2) machine learning of features for subsequent recognition. [Continues.

Sketching input for computer aided engineering

The design process often begins with a graphical description of the proposed device or system and sketching is the physical expression of the design engineer’s thinking process. Computer Aided Design is a technique in which man and machine are blended into a problem solving team, intimately coupling the best characteristics of each. Solid modelling is developed to act as the common medium between man and the computer. At present it is achieved mainly by designing with volumes and hence does not leave much room for sketching input, the traditional physical expression of the thinking process of the design engineer. This thesis describes a method of accepting isometric free hand sketching as the input to a solid model. The design engineer is allowed to make a sketch on top of a digitizer indicating (i) visible lines (ii) hidden lines (iii) construction lines (iv) centre lines (v) erased lines and (vi) redundant lines as the input. The computer then process this sketch by identifying the line segments, fitting the best possible lines, removing the erased lines, ignoring the redundant lines and finally merging the hidden lines and visible lines to form the lines in the solid in an interactive manner. The program then uses these lines and the information about the three dimensional origin of the object and produces three dimensional information such as the faces, loops, holes, rings, edges and vertices which are sufficient to build a solid model. This is achieved in the following manner. The points in the sketch is first written into a file. The computer then reads this file, breaks the group of points into sub-groups belonging to individual line segments, fits the best lines and identify the vertices in two dimensions. These improved lines in two dimensions are then merged to form the lines and vertices in the solid. These lines are then used together with the three dimensional origin (or any other point) to produce the wireframe model in three dimensions. The loops in the wireframe models are then identified and surface equations are fitted to these loops. Finally all the necessary inputs to build a B-rep solid model are produced