Search Results

Now showing 1 - 3 of 3
  • Item
    Geometric Boundary Modelling without Topological Data Structures
    (The Eurographics Association, 1986) Takala, Tapio; A.A.G. Requicha
    The Boundary Representation (BR) scheme for solid modelling is reconsidered and generalized in the paper. It is pointed out that the topological data, though usually represented separately, is derivable from the geometric data, and that there are fundamental inconsistencies between these two. The topological data structures are unnecessary or even harmful in practice as they restrict the modelling domain. New BR methodology without explicit topology is demonstrated by algorithms, which manipulate a stream of separate polygons as a solid model.
  • Item
    METAVIEWS: A Process-Oriented Approach to CAD and Graphics
    (Eurographics Association, 1988) Takala, Tapio
    A system-theoretic approach to the computer aided design (CAD) process is presented. Dependency network among objects, consisting of design operations - transactions - is formed automatically during design. The derivation process of an object, its history, can be extracted as a metalevel macro object and further edited with metadesign operations. Both top-down and bottom-up strategies are supported with this "design-by-example" method. The process-oriented methodology applies to the configuration of graphics systems also, as demonstrated with the METAVIEWS user interface.
  • Item
    THE GEOMETRIC WORKBENCH (GWB) - AN EXPERIMENTAL GEOMETRIC MODELING SYSTEM
    (The Eurographics Association, 1981) Mäntylä, Martti; Takala, Tapio; J. L. Encarnacao
    The Geometric workbench (GWB), an experimental. geometric modeling system, is described. It is based on a hybrid representation scheme, where solids are represented by CSG volume trees and boundary representations. Boundary representations are described with so called Euler operators. The operators used in GWB guarantee topological and a wide class of geometric validity constraints for the solid. upon Euler operators, sweep operators and parametrized shapes have been implemented. Representations may be stored into a data base in a procedural format. Based on the model, line figures may be drawn and volume properties of the solids may be calculated. GWB is based on a general infrastructure (workbench) approach of system construction. The beneficiance of this approach is demonstrated.