Papers by Paulos Nyirenda
Computer-Aided Design & …, Jan 1, 2006
Computer-aided Design, 2006
Four essential developments in feature modelling are discussed that solve serious shortcomings in... more Four essential developments in feature modelling are discussed that solve serious shortcomings in current feature modelling systems. First, in semantic feature modelling, it is possible to more adequately specify and maintain the meaning of features. Second, in enhanced multiple-view feature modelling, different views on a product are provided, also for conceptual and assembly design. Third, in collaborative feature modelling, several users can collaborate on the development of a product with full feature modelling functionality. Finally, in freeform feature modelling, features with freeform faces are made available. All developments are illustrated with results from research projects at Delft University of Technology, and also future developments are mentioned.
The need for more intuitive, faster and more effective tools for freeform product design is still... more The need for more intuitive, faster and more effective tools for freeform product design is still an outstanding research issue in shape modeling. We propose a new methodology in which the designer can define optimal shape modification tools for the situation at hand. The key to this method is a dialogue between the designer and the computer, in which the details of the requested shape modifier are settled. The proposed tool, called user-defined modifier (UDM), is based on recent techniques from freeform shape recognition and parameterized, template-controlled shape modification. The dialogue between user and the system is described, and the basic techniques for the UDM tool are presented as well.
Computer-aided Design, 2005
Current parametric modeling systems suffer from the persistent naming problem, which is responsib... more Current parametric modeling systems suffer from the persistent naming problem, which is responsible for the unpredictable, sometimes stunning, behavior of such systems when re-evaluating a model, even after simple editing operations. This paper claims that the problem is an inherent difficulty of the approaches taken by current parametric modeling systems, in which various persistent naming schemes end up solving only a fraction of the problem. Instead, it is argued that the rationale behind such schemes should itself be revised. Alternative approaches to define a parametric model based on persistent parametric entities can, in fact, eliminate the flaws of using references to non-persistent geometric model entities, which is the real cause of the problem. One such approach is described here, which is able to take full advantage of parametric modeling. It provides persistent entities in the parametric definition domain, which can always be consistently referred to. Basically, it proposes the use of the names of persistent feature faces, instead of the names of boundary faces, every time a reference to a face is required in a parametric definition. Furthermore, it makes use of these feature faces names in order to identify any edge of interest on the boundary representation of the model. These edge names can then be consistently referred to in further parametric definitions. Whenever ambiguities occur, e.g. due to multiple intersections, half-spaces are automatically defined by means of references associated to the features involved, which are kept in the parametric domain. An implementation of this approach is also described, which takes care of maintaining the semantics of the parametric definition of a solid object. A number of examples illustrate how user specification of modeling operations can be transparently performed through interaction with a declarative feature model.
A Generic Taxonomy for Defining Freeform Feature Classes
Computer-aided Design, 2005
Page 1. Computer-Aided Design & Applications, Vol. 2, Nos. 1-... more Page 1. Computer-Aided Design & Applications, Vol. 2, Nos. 1-4, 2005, pp 497-506 497 A Generic Taxonomy for Defining Freeform Feature Classes Paulos J. Nyirenda1, Willem F. Bronsvoort1, Thomas R. Langerak2, Yu Song2 and Joris SM Vergeest2 ...
A framework for extendable freeform surface feature modelling
Computers in Industry, 2009
Definition of Freeform Surface Feature Classes
Computer-aided Design, 2008
The success of feature modelling systems depends to a large extent on offering user-friendly ways... more The success of feature modelling systems depends to a large extent on offering user-friendly ways for specifying and varying feature models. In this paper, several new facilities are introduced for this.
In most current feature modelling systems, blends are modelled as a kind of features too. These s... more In most current feature modelling systems, blends are modelled as a kind of features too. These systems use a boundary representation (Brep) to describe the shape of a product. It is shown that the practice of basing specification of blends on conventional Breps is ineffective. A solution to this problem is introduced in which blends are described at a higher level. Blends are defined in a feature class, and instances of such a class can be added to a feature model containing relations between all features in the model. Such a semantic description of blends has several merits. In particular, constraints can be defined on them to specify important functional properties, and these properties can be maintained during the whole modelling process through validity maintenance. A new method to determine the shape of a blend, based on its properties, is also demonstrated.
Experimental study of hydrodynamic forces in mixed-flow pumps
Automation in Construction, 2004
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Papers by Paulos Nyirenda