Síntese, simulação e a internet

A síntese de imagem a partir descrições tridimensionais de ambientes virtuais, ou até de simples objectos, é um campo fascinante tanto para os investigadores da área como para o público em geral. A animação e a possibilidade de interagir com ambientes virtuais é certamente responsável por uma grande fatia deste fascínio. As aplicações derivadas da sintetização e simulação são extraordinariamente abrangentes e tem tido um sucesso impensável há uma década atrás, verificando-se que a industria do entretenimento ocupa naturalmente um lugar de destaque nesta lista. Os jogos de computador, cinema e televisão são talvez as áreas onde a sintetização e simulação é mais visível. A cultura, a ciência, o ensino, e o comércio electrónico são também áreas de potencial aplicação deste paradigma. Nestes casos a Internet é potencialmente um dos veículos de eleição para a disseminação de informação. No entanto, na Internet nem sempre se verificou essa tendência. De facto verifica-se que a utilização de gráficos tridimensionais (3D) na I. tem tido uma reputação negativa para o público em geral. Propõe-se aqui analisar o percurso deste meio no contexto da I. de forma a averiguar quais as causas desta reputação. Para terminar num tom positivo serão apresentados alguns exemplos interessantes da utilização deste paradigma de comunicação, assim como alguns casos de sucesso que podem ter um papel importante na reabilitação do 3D e consequente generalização da sua utilização

Exploring alternative devices for blind users

The ability to take advantage of the information society is becoming a must for everyone. Computer literacy is becoming more and more important for individuals as well as corporations. Therefore no efforts must be spared to integrate everyone in this new and exciting development. If for non-disabled persons this can be a challenge, for certain types of disabilities the effort of adaptation is huge. In this paper we focus on blind users. One of the current alternatives for blind users is based on specific hardware that tends to be limited in features and expansibility or very expensive. The other alternative is PC based software. This latest option, although very powerful, has also several disadvantages, namely the lack of practical mobility. In this paper we present a new approach, the PalmPCs. PalmPCs are a cheap alternative compared to the hardware mentioned above, they are truly mobile, and they are widely available today. We argue that software can be written for these devices that satisfies the needs of the majority of the blind users. A small application for WindowsCE is presented in which the interface was specifically designed for blind users.Secretariado Nacional para a Reabilitação e Integração das Pessoas com Deficiência - Programa CITE IV

GParticles: a flexible GPU-based particle library

Particle systems are widely used to create visual effects with a large number of elements (or particles). Earlier works were CPU based, while recent developments use the GPU to take advantage of the fact that, in most cases, particles are independent entities. In here, we propose a GPU-based library that focuses on extensibility and ease of use. The library allows for virtually any particle logic to be implemented, supporting fully programmable shader based effects, facilitating the definition of multiple resources and providing full control over the particle system’s simulation execution. Projects can be easily specified using XML, and extended via shaders and stubs, C functions that can be executed in between particle system’s processing stages. The examples presented illustrate the potential of the API, with multiple particle systems acting in a sequence, later extended to create custom graphic effects.COMPETE: POCI-01- 0145-FEDER-007043 and FCT – Fundaçãao para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/201

Robust reconstruction of 3D points from images

This paper presents a robust approach for 3D point recon- struction based on a set of images taken from a static scene with known, but not necessarily exact or regular, camera parameters. The points to be reconstructed are chosen from the contours of images, and a world-based formulationof the reconstruction problem and associated epipolar geom- etry is used. The result is a powerful mean of transpar- ently integrating contributions from multiple images, and increased robustness to situations such as occlusions or ap- parent contours. Two steps for adding robustness are pro- posed:cross-checking, which validates a reconstructed point taken from an image by projecting it on a special subset of the remaining images; andmerging, which fuses pairs of re- constructed points that are close in 3D space and that were initially chosen from different images. Results obtained with a synthetic scene (for ground truth comparison and error assessment), and two real scenes show the improved robustness achieved with the steps proposed

Testing AudioBrowser

We are developing AudioBrowser, a browser for visually impaired users. This paper presents a usability analysis study that was carried out on the first version of the browser. Due to the lack of availability of visually impaired users not involved with the tool's design, we had to resort to s imulate a visual impaired situation with regular sighted users. Although this may seem unrealistic we believe that this is actually a worst case scenario. The problems identified during this study are described, and proposals for the next version of the tool are put forward.Fundação para a Ciência e a Tecnologia (FCT) - POSI/SRI/41952/2001

Efficient conservative collision detection for populated virtual worlds

Large virtual worlds, with considerable level of detail are starting to emerge everywhere, from large areas of actual cities to archaeological detailed reconstructions of sites. Populating a virtual world adds an extra touch to the visualization of these worlds, but unfortunately it also brings an extra burden to the system. Several tasks are required when adding animated characters to a virtual world, such as collision detection, path planning and other AI algorithms, rendering of dynamic geometry, amongst others. In here a method for efficient and scalable conservative collision detection, that is able to deal with large scenes and thousands of avatars, is presented. This method does not perform exact collision detection, hence it is conservative. The method is suitable as a basis for path planning algorithms and other AI algorithms where an avatar is often regarded as ’something’ that can be bounded by a cylinder, or a box. The algorithm is capable of dealing with arbitrarily complex 3D worlds, and does not require any a priori knowledge of the geometry

Atmospheric scattering - state of the art

Atmospheric scattering is the natural phenomenon mainly responsible for the colours we observe in the sky. Over the years, several realistic computer graphics algorithms have been proposed in order to reproduce these colours. This state of the art is motivated by the large amount of scattered information, and by its great potential usage in a wide range of applications like flight simulators, video games and movies. This paper will cover the most important models and will present their evolution over the years. The first part contains a small introduction to the mechanics behind the light scattering phenomena. The second part will cover the earlier models, very much focused in the physical phenomenon. The third section will cover GPU based models, more focused on performance.Fundação para a Ciência e a Tecnologia (FCT

Open source debuggers and integration with a 3D engine

Debugging is always an important phase in an application life. Applications using 3D hardware accelerated graphics in general, and OpenGL in particular, are usually hard to debug since the computation is split between two processors, each with its own memory space. To be able to debug these applications one has to rely on the API's debugging mechanisms to inspect the output of the computations performed. Several tools are available for this purpose, some of them are open source. Open source tools are great to integrate in already existing projects such as 3D engines since they allow the required customizations. The goal of this paper is twofold. Firstly we provide an overview of the existing open source debugging tools for OpenGL and secondly we discuss the integration of one of such tools in an existing 3D engine.Fundação para a Ciência e a Tecnologia (FCT

Towards music-driven procedural animation

We present our approach towards the development of a framework for the creation of music-driven procedural animations. We intend to explore the potential that elementary musical features hold for driving engaging audio-visual animations. To do so, we bring forward an integrated environment where real-time musical information is available and may be flexibly used for manipulating different aspects of a dynamic animation. In general terms, our approach consists of developing a virtual scene, populated by controllable entities, termed actors, and using scripting to define how these actors' behaviour or appearance change in response to musical information. Scripting operates by establishing associations, or mappings, between musical events, such as the ringing of notes or chords, or sound information, such as the frequency spectrum, and changes in the animation. The scenario we chose to explore is comprised of two main actors: trees and wind. Trees grow in an iterative process, and may develop leaves, while swaying in response to the wind field. The wind is represented as a vector field whose configuration and strength can be altered in real-time. Scripting then allows for synchronising these changes with musical events, providing a natural sense of harmony with the accompanying music. By having real-time access to musical information, as well as control over a reactive animation we believe to have taken a first step towards exploring a novel interdisciplinary concept with vast expressive potential.This work has been supported by national funds through FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019