A Qualitative and Quantitative Evaluation of 8 Clear Sky Models

We provide a qualitative and quantitative evaluation of 8 clear sky models used in Computer Graphics. We compare the models with each other as well as with measurements and with a reference model from the physics community. After a short summary of the physics of the problem, we present the measurements and the reference model, and how we "invert" it to get the model parameters. We then give an overview of each CG model, and detail its scope, its algorithmic complexity, and its results using the same parameters as in the reference model. We also compare the models with a perceptual study. Our quantitative results confirm that the less simplifications and approximations are used to solve the physical equations, the more accurate are the results. We conclude with a discussion of the advantages and drawbacks of each model, and how to further improve their accuracy

De/construction sites: Romans and the digital playground

The Roman world as attested to archaeologically and as interacted with today has its expression in a great many computational and other media. The place of visualisation within this has been paramount. This paper argues that the process of digitally constructing the Roman world and the exploration of the resultant models are useful methods for interpretation and influential factors in the creation of a popular Roman aesthetic. Furthermore, it suggests ways in which novel computational techniques enable the systematic deconstruction of such models, in turn re-purposing the many extant representations of Roman architecture and material culture

Optimization techniques for computationally expensive rendering algorithms

Realistic rendering in computer graphics simulates the interactions of light and surfaces. While many accurate models for surface reflection and lighting, including solid surfaces and participating media have been described; most of them rely on intensive computation. Common practices such as adding constraints and assumptions can increase performance. However, they may compromise the quality of the resulting images or the variety of phenomena that can be accurately represented. In this thesis, we will focus on rendering methods that require high amounts of computational resources. Our intention is to consider several conceptually different approaches capable of reducing these requirements with only limited implications in the quality of the results. The first part of this work will study rendering of time-­¿varying participating media. Examples of this type of matter are smoke, optically thick gases and any material that, unlike the vacuum, scatters and absorbs the light that travels through it. We will focus on a subset of algorithms that approximate realistic illumination using images of real world scenes. Starting from the traditional ray marching algorithm, we will suggest and implement different optimizations that will allow performing the computation at interactive frame rates. This thesis will also analyze two different aspects of the generation of anti-­¿aliased images. One targeted to the rendering of screen-­¿space anti-­¿aliased images and the reduction of the artifacts generated in rasterized lines and edges. We expect to describe an implementation that, working as a post process, it is efficient enough to be added to existing rendering pipelines with reduced performance impact. A third method will take advantage of the limitations of the human visual system (HVS) to reduce the resources required to render temporally antialiased images. While film and digital cameras naturally produce motion blur, rendering pipelines need to explicitly simulate it. This process is known to be one of the most important burdens for every rendering pipeline. Motivated by this, we plan to run a series of psychophysical experiments targeted at identifying groups of motion-­¿blurred images that are perceptually equivalent. A possible outcome is the proposal of criteria that may lead to reductions of the rendering budgets

Virtual Reality Games for Motor Rehabilitation

This paper presents a fuzzy logic based method to track user satisfaction without the need for devices to monitor users physiological conditions. User satisfaction is the key to any product’s acceptance; computer applications and video games provide a unique opportunity to provide a tailored environment for each user to better suit their needs. We have implemented a non-adaptive fuzzy logic model of emotion, based on the emotional component of the Fuzzy Logic Adaptive Model of Emotion (FLAME) proposed by El-Nasr, to estimate player emotion in UnrealTournament 2004. In this paper we describe the implementation of this system and present the results of one of several play tests. Our research contradicts the current literature that suggests physiological measurements are needed. We show that it is possible to use a software only method to estimate user emotion

An approximation to multiple scattering in volumetric illumination towards real-time rendering

Many volumetric illumination techniques for volume rendering were developed through out the years. However, there are still many constraints regarding the computation of multiple scattering path tracing in real-time applications due to its natural complexity and scale. Path tracing with multiple scattering support can produce physically correct results but suffers from noise and low convergence rates. This work proposes a new real-time algorithm to approximate multiple scattering, usually only available in offline rendering production, to real-time. Our approach explores the human perceptual system to speed up computation. Given two images, we use a CIE metric stating that the two will be perceived as similar to the human eye if the Euclidean distance between the two images in CIELAB color space is smaller than 2.3. Hence, we use this premise to guide our in vestigations when changing ray and bounce parameters in our renderer. Our results show that we can reduce from 105 to 104 Samples Per Pixel (SPP) with a negligible perceptual difference between both results, allowing us to cut rendering times by 10 whenever we divide SPP by 10. Similarly, we can reduce the number of bounces from 1000 to 100 with a negligible perceptual difference while reducing rendering times by almost half. We also propose a new algorithm in real-time, Lobe Estimator, that approximates these behaviors and parameters while performing twice as faster as the classic Ray Marching technique.Muitas técnicas de ilmuninação volumétrica foram desenvolvidas ao longo dos anos. Entretanto, ainda há muitas restrições na computação de multiple scattering em aplicações de tempo real usando path tracing, devido à sua complexidade e escala. Path tracing com suporte a multiple scattering é capaz de produzir resultados fisicamente corretos, mas sofre de ruídos e baixa taixa de convergência. Portanto, este trabalho propõe um novo algoritmo de tempo real para aproximar multiple scattering, usado em offline rendering. Nossa abordagem irá explorar o sistema perceptual visual humano para acelerar a computação. A partir de duas imagens, nós usamos a métrica da CIE que afirma que duas imagens são percebidas como similar ao olho humano se a distância Euclidiana das duas imagens no espaço de cores CIELAB for menor que 2.3. Dessa forma, nós usamos essa premissa para guiar nossas investigações quando alterando os parâmetros de Samples Per Pixel (SPP) e bounces nos renderizadores. Nossos resultados mostram que podemos redu zir de 105 para 104 Samples Per Pixel (SPP) com uma diferença perceptual negligenciável entre ambos paramêtros, permitindo reduzir o tempo de renderização por 10 a cada vez que dividimos o SPP por 10. Similarmente, nós podemos reduzir o número de bounces de 1000 para 100 com uma diferença perceptual negligenciável, enquanto reduzindo o tempo de renderização por quase metade. Nós também propusemos um novo algoritmo em tempo real, Lobe Estimator, que permite aproximar esses comportamentos e paramê tros enquanto permformando duas vezes mais rápido que o clássico Ray Marching

Analysis domain model for shared virtual environments

The field of shared virtual environments, which also encompasses online games and social 3D environments, has a system landscape consisting of multiple solutions that share great functional overlap. However, there is little system interoperability between the different solutions. A shared virtual environment has an associated problem domain that is highly complex raising difficult challenges to the development process, starting with the architectural design of the underlying system. This paper has two main contributions. The first contribution is a broad domain analysis of shared virtual environments, which enables developers to have a better understanding of the whole rather than the part(s). The second contribution is a reference domain model for discussing and describing solutions - the Analysis Domain Model

Media Presence and Inner Presence: The Sense of Presence in Virtual Reality Technologies

Abstract. Presence is widely accepted as the key concept to be considered in any research involving human interaction with Virtual Reality (VR). Since its original description, the concept of presence has developed over the past decade to be considered by many researchers as the essence of any experience in a virtual environment. The VR generating systems comprise two main parts: a technological component and a psychological experience. The different relevance given to them produced two different but coexisting visions of presence: the rationalist and the psychological/ecological points of view. The rationalist point of view considers a VR system as a collection of specific machines with the necessity of the inclusion \ud of the concept of presence. The researchers agreeing with this approach describe the sense of presence as a function of the experience of a given medium (Media Presence). The main result of this approach is the definition of presence as the perceptual illusion of non-mediation produced by means of the disappearance of the medium from the conscious attention of the subject. At the other extreme, there \ud is the psychological or ecological perspective (Inner Presence). Specifically, this perspective considers presence as a neuropsychological phenomenon, evolved from the interplay of our biological and cultural inheritance, whose goal is the control of the human activity. \ud Given its key role and the rate at which new approaches to understanding and examining presence are appearing, this chapter draws together current research on presence to provide an up to date overview of the most widely accepted approaches to its understanding and measurement

Developing serious games for cultural heritage: a state-of-the-art review

Although the widespread use of gaming for leisure purposes has been well documented, the use of games to support cultural heritage purposes, such as historical teaching and learning, or for enhancing museum visits, has been less well considered. The state-of-the-art in serious game technology is identical to that of the state-of-the-art in entertainment games technology. As a result, the field of serious heritage games concerns itself with recent advances in computer games, real-time computer graphics, virtual and augmented reality and artificial intelligence. On the other hand, the main strengths of serious gaming applications may be generalised as being in the areas of communication, visual expression of information, collaboration mechanisms, interactivity and entertainment. In this report, we will focus on the state-of-the-art with respect to the theories, methods and technologies used in serious heritage games. We provide an overview of existing literature of relevance to the domain, discuss the strengths and weaknesses of the described methods and point out unsolved problems and challenges. In addition, several case studies illustrating the application of methods and technologies used in cultural heritage are presented