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End date: 1989 × Has files: true × Start date: 1980 × Author: Takala, Tapio ×

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Now showing 1 - 5 of 5
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    Partially Ordered Search Indices in the Organizationof a Fixed Hierarchy
    (The Eurographics Association, 1987) Skyttä, Jorma; Takala, Tapio; Fons Kuijk and Wolfgang Strasser
    "IntroductionThe mapping of even very advanced algorithms directly to hardware does not typically bring good results as these algorithms are originally designed for sequential processing. However, the power of the modern integration technology lies in its ability to produce high volumes of reasonably complex elements at moderate cost. For utilization of these possibilities the algorithms and data structures already developed must be redesigned for parallel computation."
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    A Distributed Data Model for Raytracing
    (The Eurographics Association, 1988) Skyttä, Jorma; Takala, Tapio; A. A. M.Kuijk
    Ray tracing is a superior method for producing realistic images. It can take into account all natural phenomena covered by classical ray optics in image formation, and that without any extra modeling effort. The main disadvantage is its high cost in terms of computer time. Production of ray traced images of reasonably complex scenes takes long in real time with a moderate general purpose computer [Whi80).The basic idea of ray tracing is the brute force algorithm for simulating the path of a ray of light in the whole model space. As no global information of the model is used to anticipate the interactions of the ray with model elements, every ray must be tested against every object and most of the processing time is consumed to ray-object intersection calculation. At each intersection found the ray is divided into reflected and refracted components and into a ray directed to each light source to produce shadows. Higher quality images need more pixels to be calculated and the number of elements in a scene grows linearly with model complexity, leading to steep increase of the computational complexity of the whole problem.
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    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.
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    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.
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    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.