Percorrer por autor "Chalmers, Alan"
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- High dynamic range - a gateway for predictive ancient lightingPublication . Gonçalves, Alexandrino José Marques; Magalhães, Luís; Moura, João; Chalmers, AlanIn the last few years, the number of projects involving historical reconstruction has increased significantly. Recent technologies have proven a powerful tool for a better understanding of our cultural heritage through which to attain a glimpse of the environments in which our ancestors lived. However, to accomplish such a purpose, these reconstructions should be presented to us as they may really have been perceived by a local inhabitant, according to the illumination and materials used back then and, equally important, the characteristics of the human visual system. The human visual system has a remarkable ability to adjust itself to almost all everyday scenarios. This is particularly evident in extreme lighting conditions, such as bright light or dark environments. However, a major portion of the visible spectra captured by our visual system cannot be represented in most display devices. High dynamic range imagery is a field of research which is developing techniques to correct such inaccuracies. This new viewing paradigm is perfectly suited for archaeological interpretation, since its high contrast and chromaticity can present us with an enhanced viewing experience, closer to what an inhabitant of that era may have seen. In this article we present a case study of the reconstruction of a Roman site. We generate high dynamic range images of mosaics and frescoes from one of the most impressive monuments in the ruins of Conimbriga, Portugal, an ancient city of the Roman Empire. To achieve the requisite level of precision, in addition to having a precise geometric 3D model, it is crucial to integrate in the virtual simulation authentic physical data of the light used in the period under consideration. Therefore, in order to create a realistic physical-based environment, we use in our lighting simulations real data obtained from simulated Roman luminaries of that time.
- Illuminating the past: state of the artPublication . Happa, Jassim; Mudge, Mark; Debattista, Kurt; Artusi, Alessandro; Gonçalves, Alexandrino; Chalmers, AlanVirtual reconstruction and representation of historical environments and objects have been of research interest for nearly two decades. Physically based and historically accurate illumination allows archaeologists and historians to authentically visualise a past environment to deduce new knowledge. This report reviews the current state of illuminating cultural heritage sites and objects using computer graphics for scientific, preservation and research purposes. We present the most noteworthy and up-to-date examples of reconstructions employing appropriate illumination models in object and image space, and in the visual perception domain. Finally, we also discuss the difficulties in rendering, documentation, validation and identify probable research challenges for the future. The report is aimed for researchers new to cultural heritage reconstruction who wish to learn about methods to illuminate the past.
- Metodologia para a geração de imagens High Dynamic Range em iluminação romanaPublication . Gonçalves, Alexandrino José Marques; Magalhães, Luís Gonzaga; Moura, João Paulo; Chalmers, AlanNum futuro muito próximo, o modo como veremos conteúdos num qualquer dispositivo de visualização irá sofrer profundas alterações. A luz captada pelo olho humano num simples passeio pela praia num radioso dia de sol, pode atingir valores de intensidade e cromaticidade verdadeiramente astronómicos. No entanto, grande parte dessa amplitude dinâmica não tem representação possível no modelo RGB, usado praticamente na totalidade dos dispositivos de visualização actuais. High Dynamic Range (HDR) é uma área de investigação que se dedica ao estudo de formas e métodos que visam suprir essa lacuna. Para atingir tal intento, têm sido desenvolvidas novas técnicas para a geração, armazenamento e representação de imagens que consigam preservar a elevada amplitude dinâmica captada pelo Sistema Visual Humano. Neste artigo apresentamos uma metodologia de trabalho que utiliza este novo paradigma de visualização onde o seu potencial é verdadeiramente apropriado, a arqueologia. A Casa dos Repuxos é o espaço mais belo e imponente existente nas ruínas de Conimbriga (Portugal) e que ainda hoje preserva alguns dos frescos e mosaicos originais. O nosso objectivo centra-se na geração de imagens HDR desses frescos e mosaicos iluminados por luminárias desse período, de modo a que a experiência visual seja a mais próxima possível de um habitante daquela mesma casa.
- Procedural Virtual WorldsPublication . Rodrigues, Nuno; Magalhães, Luís; Moura, João Paulo; Chalmers, Alan; Santos, Filipe; Morgado, LeonelWith the increasing demand for more complex and larger models in different fields, such as the design of virtual worlds, video games, and computer animated movies, the need to generate them automatically has become more necessary than ever. Manual tools are no longer sufficient to match this rising need, and the impact that automatic tools may have within these fields is essential and may lead to an adoption of virtual worlds in a growing number of applications. Indeed, it is possible to eliminate most of the effort associated with the creation of such environments, by providing tools that may generate “massive” 3D content automatically. In consequence these tools may lead to an exponential growth of virtual environments and represent an important turn into the design of realistic virtual cities, which may have a huge impact on virtual world users. This chapter discusses the very complex issue of where and when procedural modelling may be used and presents some solutions and methods that have been successfully used in the aforementioned fields of application.
- A survey on HDR visualization on mobile devicesPublication . Magalhães, Luis; Bessa, Maximino; Urbano, Carlos; Melo, Miguel; Peres, Emanuel; Chalmers, Alan; Pasi SaarikkoThere is a vast body of literature concerning the capture, storing, transmission and display of High Dynamic Range (HDR) imaging. Nevertheless, there are few works that try to address the problem of getting HDR on mobile devices. Their hardware limitations, such as processing power, storage space, graphics capabilities and screen characteristics, transform that problem in a big challenge. However, since more and more HDR content is being produced and given that in a few years it can become a standard, it is necessary to provide the means to visualize HDR images and video on mobile devices. The main goal of this paper is to present a survey on HDR visualization approaches and techniques developed specifically for mobile devices. To understand what are the main challenges that need to be addressed in order to visualize HDR on mobile devices, an overview of their main characteristics is given. The very low dynamic range of most of mobile devices' displays implies that a tone mapping operator (TMO) must be applied in order to visualize the HDR content. The current status of the research on TMO will be presented and analyzed, a special attention will be given to the ones that were developed taking in account the limited characteristics of the mobile devices' displays. Another important issue is visualization quality assessment, meaning visualize HDR content without losing the main characteristics of the original HDR content. Thus, evaluation studies of HDR content visualization on mobile devices will be presented and their results analyzed.
- Visualização de espaços arqueológicos usando High Dynamic RangePublication . Gonçalves, Alexandrino José Marques; Magalhães, Luís Gonzaga; Moura, João Paulo; Chalmers, AlanÉ hoje amplamente reconhecido que os sistemas informáticos desempenham um papel fundamental no estudo e interpretação de espaços arqueológicos. Uma das suas principais áreas de aplicação é, seguramente, a reconstrução virtual de ambientes históricos, em particular os que já não existem. Neste domínio, a forma como visualizamos tais ambientes é particularmente importante para uma correcta interpretação arqueológica do espaço em causa, seja ele qual for. No entanto, a busca pelo perfeccionismo na representação visual de um qualquer cenário, está estritamente relacionada com a tecnologia de visualização usada para o efeito. O Sistema Visual Humano tem, na realidade, uma capacidade extraordinária e consegue captar valores de intensidade e cromaticidade verdadeiramente astronómicos. No entanto, grande parte dessa amplitude dinâmica não tem representação possível no modelo RGB, usado praticamente na totalidade dos dispositivos de visualização actuais. High Dynamic Range (HDR) é uma área de investigação que se dedica ao estudo de formas e métodos que visam suprir essa lacuna. Para atingir tal intento, têm sido desenvolvidas novas técnicas para a geração, armazenamento e representação de imagens que consigam preservar a (elevada) amplitude dinâmica captada pelo Sistema Visual Humano. Neste artigo apresentamos uma metodologia de trabalho que utiliza este novo paradigma de visualização onde o seu potencial se apropria verdadeiramente, a arqueologia. Desse modo propomo-nos gerar imagens de um dos mais belos e imponentes espaços existente nas ruínas da antiga cidade Romana de Conimbriga, a Casa dos Repuxos. Para tal, iremos simular a visualização, com recurso a imagens HDR, dos frescos e mosaicos lá existentes usando luminárias da época.