Introduction:

Computer Graphics, through the design, manipulation and processing of extremely varied types of pictographic data using computers, has provided a rich vision of innovative applications. As a scientific endeavour, it has fostered such diverse areas as multimedia, virtual environments, augmented reality, tele-presence, user-friendly and interactive human-computer interfaces, simulation and the visualization of complex information.

In Portugal, research, development and education in the area of Computer Graphics have a long tradition. In fact, the Portuguese Group of Computer Graphics/Eurographics Portuguese Chapter (GPCG - Grupo Português de Computação Gráfica), has been organising since 1988 a series of scientific events, referred to as the Portuguese Symposium on Computer Graphics (Encontro Português de Computação Gráfica), which will now enter, during 2005, in its 13th edition. In the last editions, the Symposium has explored the synergies between Computer Graphics, Image Processing, and Computer Vision in emergent application areas. The convergence between these three areas is increasingly important and enabler of interesting work, particularly in classifying objects in natural scenes (e.g., in management of natural resources) or in providing Augmented Reality, which allows the user to see the real world with the registration of 2D/3D virtual objects, thus complementing the reality rather than replacing it.

In this context, the Portuguese Community of Computer Graphics, here represented by the GPCG and its Executive board, believes that the moment has arrived were it is important to disseminate in proper National and International fora, the most recent advances in Computer Graphics in Portugal, performed by Portuguese researchers in National and International R&D institutes and companies. That has been the challenge behind this special issue of the VIRTUAL Journal (virtual.inesc.pt, November/December 2004): to disseminate outputs/progress/ideas of innovative National and International research activities performed by Portuguese researchers in Computer Graphics. With this purpose in mind, the Journal editing board has launched a call for extended versions of fourteen selected papers of the 12th Portuguese Symposium on Computer Graphics, which was held in ISEP, Instituto Superior de Engenharia do Porto, from 8th-10th October 2003. These extended papers, written in English, were peer reviewed by the Journal advisory board and thirteen among them were selected for publication. The Journal is organized in the following chapters: Geometric Modelling, Multimedia and Graphical Visualization, Virtual Environments and Augmented Reality.

This special edition is the result of much hard work and sincere devotion of a large number of people as well as the support of several institutions. The Editor in Chief and the Guest Editors, would like to express a word of thanks to the contributors of this publication: first of all, to the authors of the submitted extended works, for their motivation, commitment and effort put into the writing of their papers; to the members of the advisory board, for the attention dedicated to the peer review of the submitted works, and, in particular, to Ana Rita Leitão and Frederico Figueiredo, for their professional commitment in assuming the numerous tasks related with the final production of such a publication. We would finally like to thank all the people and institutions that have supported this edition of the Virtual Journal/Portuguese Journal of Computer Graphics - Advances in Computer Graphics in Portugal: Lisbon, November 2004

Joaquim Jorge
Adérito Fernandes Marcos
José Miguel Salles Dias