Eva Cerezo

A survey on participating media rendering techniques

Rendering participating media is important for a number of domains, ranging from commercial applications (entertainment, virtual reality) to simulation systems (driving, flying, and space simulators) and safety analyses (driving conditions, sign visibility). This article surveys global illumination algorithms for environments including participating media. It reviews both appearance-based and physically-based media methods, including the single-scattering and the more general multiple-scattering techniques. The objective of the survey is the characterization of all these methods: identification of their base techniques, assumptions, limitations, and range of utilization. It concludes with some reflections about the suitability of the methods depending on the specific application involved, and possible future research lines.

Bringing tabletop technology to all: evaluating a tangible farm game with kindergarten and special needs children

The tangible interaction approach has in recent years become a promising alternative to multitouch tabletops for very young children. Children learning with tangible user interfaces can benefit from the same pedagogical values as learning with materials in physical play. The NIKVision tabletop and games have been designed to provide leisure and fun while reinforcing physical manipulation and co-located gaming for young children (3- to 6-year-olds). Interaction is provided in NIKVision by the handling of conventional toys and computer augmentation on a table surface. First of all, the paper sets out the results of a summative evaluation carried out in nurseries and schools summarising the performance of the tabletop in terms of usability, user experience and physical and co-located gaming. Secondly, the paper presents an evaluation carried out in a special education school with children with cognitive disabilities, in an attempt to widen the range of possible beneficiaries of tangible interfaces. The challenge in this case is to ensure children’s comprehension of the game and to adequately combine feedback on the application with teacher interventions. In fact, the initial results reinforce the idea of not trying to substitute but rather to assist teachers and emphasise the possibilities offered by the tabletop as a tool to promote student autonomy.

Chaos and Graphics: Maxine: A platform for embodied animated agents

This paper presents a powerful animation engine for developing applications with embodied animated agents called Maxine. The engine, based on open source tools, allows management of scenes and virtual characters, and pays special attention to multimodal and emotional interaction with the user. Virtual actors are endowed with facial expressions, lip-synch, emotional voice, and they can vary their answers depending on their own emotional state and the relationship with the user during conversation. Maxine virtual agents have been used in several applications: a virtual presenter was employed in MaxinePPT, a specific application developed to allow non-programmers to create 3D presentations easily using classical PowerPoint presentations; a virtual character was also used as an interactive interface to communicate with and control a domotic environment; finally, an interactive pedagogical agent was used to simplify and improve the teaching and practice of Computer Graphics subjects.

Computer animation: from avatars to unrestricted autonomous actors (A survey on replication and modelling mechanisms)

Abstract Dealing with synthetic actors who move and behave realistically in virtual environments is a task which involves different disciplines like Mechanics, Physics, Robotics, Artificial Intelligence, Artificial Life, Biology, Cognitive Sciences and so on. In this paper we use the nature of the information required for controlling actors’ motion and behaviour to propose a new classification of synthetic actors. A description of the different motion and behaviour techniques is presented. A set of Internet adresses of the most relevant research groups, commercial companies and other related sites in this area is also given.

Bridging the gap between children and tabletop designers

This paper presents a case study of the design lifecycle of games involving tangible interaction toys handled on an active surface tabletop. The games are oriented to 3--6 year old children, so special care has been taken in the methods used to involve them in a child-centered design lifecycle. The iterative nature of this design paradigm was supported by frequent test sessions where data relating to usability and fun was captured and analyzed in order to guide successive design iterations until a finished product was achieved. The aim is to guide designers intending to involve children in similar tabletop game creation projects. Details are given of how data collected from test sessions with children revealed usability problems and helped to create, evolve and improve the games.

Motion and behaviour modelling: state of art and new trends

The main task of a computer animator is to make the objects of a purely synthetic 3D world move realistically. The great number of computer animation techniques that already exist and the new ones that are continuously appearing, are the result of a multidisciplinary exchange of ideas. Our main goal has been to provide a classification of computer animation systems focused on motion and behaviour modelling from the point of view of control techniques. We also present the historical evolution in these areas, providing an extensive bibliography and highlighting some historical milestones. Finally, a set of Internet adresses of the most relevant research groups in this area present on the Web is also given.

Facial emotional classification: from a discrete perspective to a continuous emotional space

User emotion detection is a very useful input to develop affective computing strategies in modern human computer interaction. In this paper, an effective system for facial emotional classification is described. The main distinguishing feature of our work is that the system does not simply provide a classification in terms of a set of discrete emotional labels, but that it operates in a continuous 2D emotional space enabling a wide range of intermediary emotional states to be obtained. As output, an expressional face is represented as a point in a 2D space characterized by evaluation and activation factors. The classification method is based on a novel combination of five classifiers and takes into consideration human assessment for the evaluation of the results. The system has been tested with an extensive universal database so that it is capable of analyzing any subject, male or female of any age and ethnicity. The results are very encouraging and show that our classification strategy is consistent with human brain emotional classification mechanisms.

Sensing facial emotions in a continuous 2D affective space

The interpretation of user facial expressions is a very useful method for emotional sensing and it constitutes an indispensable part of affective Human Computer Interface designs. Facial expressions are often classified into one of several basic emotion categories. This categorical approach seems poor to treat faces with blended emotions, as well as to measure the intensity of a given emotion. This paper presents an effective system for facial emotional classification, where facial expressions are evaluated with a psychological 2-dimensional continuous affective approach. At its output, an expressional face is represented as a point in a 2D space characterized by evaluation and activation factors. The proposed system first starts with a classification method in discrete categories based on a novel combination of classifiers, that is subsequently mapped in a 2D space in order to be able to consider intermediate emotional states. The system has been tested with an extensive universal database and human assessment has been taken into consideration in the evaluation of results.

User-oriented design and tangible interaction for kindergarten children

This paper describes a tabletop prototype that allows kindergarten children to take the benefits of the new pedagogical possibilities that tangible interaction and tabletop technologies offer to manipulative learning. After analyzing childrens cognitive and psychomotorial skills, we have designed and tuned a prototype game suitable for children aged 3 to 4 years old. Our prototype uniquely combines low cost tangible interaction and tabletop technology with tutored learning. The design has been based on observations of the children using the technology, letting them freely play with the application during three play sessions. These observational sessions informed the design decisions for the game whilst also confirming the childrens enjoyment with the prototype.

Technical section: Implementation of a method of curved ray tracing for inhomogeneous atmospheres

In this paper, we describe a method of curved ray tracing for depicting various phenomena which may arise, under certain conditions, when light propagates through an inhomogeneous atmosphere. As example applications, the method of curved ray tracing will be applied to the phenomena of the distortion of the line of horizon, road mirages, sunsets and distortion of images caused by fire. Even though the scenes used are simple, the method is general and can be applied to any media in which the index of refraction is a function of the position.