António Augusto de Sousa

Lighting design: a goal based approach using optimisation

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 geometry 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.

High Performance Computing for Computational Science — VECPAR 2002

A methodology to simulate large-scale fluid-structure interaction problems on parallel machines has been developed. Particular emphasis was placed on shock-structure interaction problems. For the fluid, a high-resolution FEM-FCT solver based on unstructured grids is used. The surface motion is handled either by moving, body fitted grids, or via surface embedding. For the structure, a Lagrangean large-deformation finite element code is employed. The coupled system is solved using a loose coupling algorithm, with position and velocity interpolation and force projection. Several examples, run on parallel machines, demonstrate the range of applicability of the proposed methodology.

Expeditious Modelling of Virtual Urban Environments with Geospatial L‐systems

L‐systems have been used in Computer Graphics, namely for modelling plants, as well as in a few experiments to model urban environments. However, the lack of geospatial awareness is a limitation and in spite of some developments like open L‐systems, that introduced the ability to communicate with the environment, there was a need for more flexibility. This paper presents Geospatial L‐systems, a new extension of L‐systems that incorporates geospatial awareness, and shows an application in the area of expeditious modelling of urban environments. A modelling system, named XL3D, generates virtual urban environments automatically from a XML based document that contains a modelling specification and accesses data sources in an interoperable way. The integration of geospatial L‐systems in this modelling system has increased the potential for automation and the potential to generate virtual urban environments with a higher level of detail and visual fidelity, with a lower level of complexity of the modelling processes. These facts are shown in a case study where a virtual urban environment, taken from an area in the Porto downtown, is generated by this solution.

Graphical control of autonomous, virtual vehicles

This paper presents some of the developments we made with the goal of allowing a friendly control and simulation of a large number of autonomous agents based in behavior in interactive real-time systems. Our work has been specially oriented to the simulation and control of autonomous vehicles and pedestrians in the preparation of scenarios to driving simulation experiments in the DriS simulator. Because every element is intrinsically autonomous, only a few of them are usually addressed to implement the desired study event. Also, because our model is autonomous and controllable, we can use the same model in the implementation of both environment traffic and controlled vehicles. Our scripting language is based in Grafcet, a well known graphical language used in the specification and programming of industrial controllers. Our technique allows the imposition of both short time orders and long time goals to each autonomous element. Orders can be triggered reactively using sensors that monitor the state of virtual traffic and configurable timers that generate all the necessary fixed and variable time events.

Special Section on CANS: Sketch express: A sketching interface for facial animation

One of the most challenging tasks for an animator is to quickly create convincing facial expressions. Finding an effective control interface to manipulate facial geometry has traditionally required experienced users (usually technical directors), who create and place the necessary animation controls. Here we present our sketching interface control system, designed to reduce the time and effort necessary to create facial animations. Inspired in the way artists draw, where simple strokes define the shape of an object, our approach allows the user to sketch such strokes either directly on the 3D mesh or on two different types of canvas: a 2D fixed canvas or more flexible 2.5D dynamic screen-aligned billboards. In all cases, the strokes do not control the geometry of the face, but the underlying animation rig instead, allowing direct manipulation of the rig elements. Additionally, we show how the strokes can be easily reused in different characters, allowing retargeting of poses on several models. We illustrate our interactive approach using varied facial models of different styles showing that first time users typically create appealing 3D poses and animations in just a few minutes. We also present in this article the results of a user study. We deploy our method in an application for an artistic purpose. Our system has also been used in a pioneer serious game context, where the goal was to teach people with Autism Spectrum Disorders (ASD) to recognize facial emotions, using real time synthesis and automatic facial expression analysis.

A Scalable Implementation of an Interactive Increasing Realism Ray-Tracing Algorithm

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.

A Spatio-temporal Database System Based on TimeDB and Oracle Spatial

The importance of the spatial component of data items has been long recognized and gave rise to a successful line of research and development in Geographic Information Systems (GIS). In many application domains it is also essential to deal with the evolution of data along time and to integrate spatial, temporal and other aspects of the information domain in an expressive and operationally effective manner. Until recently, temporal solutions provided by spatial database systems were semi-temporal approaches lacking full temporal support. As a consequence, most spatial database systems manage snapshots of the present state of facts without fully exploiting historical temporal aspects. This paper provides preliminary results on a spatiotemporal database implementation. The proposed system builds on existing database technologies, TimeDB and Oracle Spatial, for temporal and spatial support, respectively. The justification for the choice of these technologies is given, based on the state of the art in spatial and temporal database research. The integration of the spatial and temporal components is achieved with the extension of the TimeDB implementation layer. A set of goals has been established in order to cover both the integration of the spatial support and the enforcement of the temporal requirements in the extended system. Issues and solutions are presented and illustrative examples show the use of the implemented functionalities.

Adaptation and validation of the igroup presence questionnaire ipq in a portuguese sample

The present study aims (a) to translate and adapt the Igroup Presence Questionnaire (IPQ) to the Portuguese context (semantic equivalence/ conceptual and content validity) and (b) to examine its psychometric properties (reliability and factorial validity). The sample consisted of 478 subjects (285 males and 193 females). The fidelity of the factors varied between 0.53 and 0.83. The confirmatory factor analysis results produced a 14-item version of IPQ-PT, accepting covariance between residual errors of some items of the instrument, as the best structural representation of the data analyzed. The CFA was conducted based on a three-variable model. The fit indexes obtained were X2/df = 2.647, GFI = .948, CFI = .941, RSMEA = .059, and AIC = 254. These values demonstrate that the proposed Portuguese translation of the IPQ maintains its original validity, demonstrating it to be a robust questionnaire to measure the sense of presence in virtual reality studies. It is therefore recommended for use in presence research when using Portuguese samples.

Sketch express: facial expressions made easy

Finding an effective control interface to manipulate complex geometric objects has traditionally relied on experienced users to place the animation controls. This process, whether for key framed or for motion captured animation, takes a lot of time and effort. We introduce a novel sketching interface control system inspired in the way artists draw, in which a stroke defines the shape of an object and reflects the users intention. We also introduce the canvas, a 2D drawing region where the users can make their strokes, which determines the domain of interaction with the object. We show that the combination of strokes and canvases provides a new way to manipulate the shape of an implicit volume in space. And most importantly, it is independent from the 3D model rig. The strokes can be easily stored and reused in other characters, allowing retargeting of poses. Our interactive approach is illustrated using facial models of different styles. As a result, we allow rapid manipulation of 3D faces on the fly in a very intuitive and interactive way. Our informal study showed that first time users typically master the system within seconds, creating appealing 3D poses and animations in just a few minutes.

Best multiple-view selection for the visualization of urban rescue simulations

In this paper we address the problem of automatically computing a set of views over a simulated three dimensional environment. The viewing system aims at, for each moment, supplying the user with the most pertinent information in order to allow a good understanding of the evolving environment. Our approach relies on an innovative optimization architecture that enables intelligent optimization techniques based on simulated annealing and genetic algorithms. Reported experiments were performed in urban rescue scenarios from the RoboCup Rescue Domain. We outline the possible extension of the proposed architecture to other visualization problems and argue on how several problems within the fields of Visualization and Rendering can benefit from it.