Abstract

Abstract

Abstract
The complex and extensive nature of urban environments creates difficulties to the task of generating virtual models. Thus a great effort in terms of human resources, time and money is needed. Nevertheless a large number of professionals and institutions devout efforts to gather and analyse data from these urban environments. As data is usually stored in a digital format, it becomes a valuable asset to incorporate it in the modelling process of virtual environments. This paper presents a three-dimensional modelling system with interoperable access to data in diverse formats and digital support, drived by an L-system based modelling process that automatically generates initial solutions for virtual environments, which can be incrementally improved.

Abstract
There is a need for reliable lighting design applications because available tools are limited and inappropriate for interactive or creative use. Architects and lighting designers need those applications to define, predict, test and validate lighting solutions for their problems. We present a new approach to the lighting design problem based on a methodology that includes the gelometry of the scene, the properties of materials and the design goals. It is possible to obtain luminaire characteristics or other kind of results that maximise the attainment of the design goals, which may include different types of constraints or objectives (lighting, geometrical or others). The main goal, in our approach, is to improve the lighting design cycle. In this work we discuss the use of optimisation in lighting design, describe the implementation of the methodology, present real-world based examples and analyse in detail some of the complex technical problems associated and speculate on how to overcome them.

Abstract
Ray-Tracing is a well known algorithm that simulates the reflection and refraction of light rays in the objects surfaces, beginning with rays sent from the view point. Each ray has to be tested against objects in the 3D scene and this is very time consuming. This paper describes one parallel solution. It is oriented to a general network, where each processor manages data and tasks and shares them with the others to optimise common resources utilisation. In this context, a Virtual Sharing Memory (VSM) is used and an efficient load balancing strategy can be implemented. With this approach, the amount of messages in the network tends to increase and strategies to reduce them are needed. Schemes to optimise remote accesses to data have been developed, namely a special type of multicast message addressing named InPathTo. © Springer-Verlag Berlin Heidelberg 1997.

Abstract
Three-dimensional graphical applications can provide an added value to Location Based Mobile Services (LBMS). This is particularly true for the applications related to urban environments, which can interactively present three-dimensional models to the user, visualized in accordance to his location. Modelling an urban environment is mainly a manual procedure and so it can become a difficult, tedious and time consuming task, due to the many different geometries, textures, details, etc, involved in the urban structures. This paper presents the XL3D modelling system that provides, in an automatic fashion, three-dimensional models of urban areas to be used in a LBMS Project. The XL3D modelling system is based on interoperable access to digital data, in diverse formats, accessing XML documents or invoking Web services in a distributed architecture. The system is driven by L-systems based modelling processes that automatically generate three-dimensional models of urban environments, specified in a declarative mode using documents based on an XML Schema, also called XL3D. Copyright © 2005 by the Association for Computing Machinery, Inc.