Concepção de experiências psicofísicas para visualização de imagens HDR em dispositivos móveis

Nos últimos catorze anos, foram muitas as técnicas desenvolvidas para redução da gama dinâmica de uma cena por forma a melhor mostrá-la em dispositivos de visualização comuns. Têm sido realizadas diversas experiências psicofísicas por forma a classificar num ranking os operadores de tone mapping (TMOs) mas, até à data, ninguém ousou testá-los em dispositivos com ecrãs pequenos como os PDAs (Personal Digital Assistants). O nosso objectivo consiste na escolha do(s) algoritmo(s) que melhor operam neste tipo de dispositivos. Esta decisão basear-se-á em resultados de experiências psicofísicas que serão realizadas. No entanto, é nossa preocupação conceber e conduzir tais experiências com o máximo cuidado e rigor. Assim, neste trabalho definimos as condições experimentais para avaliação dos TMOs em dispositivos com muito baixa gama dinâmica (VLDR – Very Low Dynamic Range)

Photographic tone reproduction for digital images

technical reportA classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print. This tone reproduction problem is also faced by computer graphics practitioners who must map digital images to a low dynamic range print or screen. The work presented in this paper leverages the time-tested techniques of photographic practice to develop a new tone reproduction operator. In particular, we use and extend the techniques developed by Ansel Adams to deal with digital images. The resulting algorithm is simple and is shown to produce good results for the wide variety of images that we have tested

Tone Reproduction in Virtual Reality

High dynamic range imaging has become very popular over the years in the field of computer graphics and games. The process of tone reproduction compresses the dynamic range of brightness in a scene to the lower range of display devices, thus making it an essential process in the graphics rendering pipeline. Various tone mapping operators have been tested for static viewing conditions. However, perceptual and temporal adaptation may vary for immersive viewing in a Virtual Reality environment. This thesis implements Ward et al. model (1994), Ward et al. model, Histogram Adjustment (1997) and Irawan, Ferwerda and Marschner model (2005) for static and immersive inputs. Faculty and students from the college took part in a personal survey to rate the tone mapped results based on their level of resemblance to real-life outdoor environments as well as the level of visibility in the lighter and darker regions. The proposed hypothesis states that immersion produces a measurable effect on our preference for a suitable tone reproduction model. This hypothesis is tested with the help of null hypothesis testing methods and some regression analysis on the data gathered from the survey

Desenvolvimento de um operador de tone mapping para dispositivos com ecrã pequeno

Actas de 17º Encontro Português de Computação GráficaDada a forte divulgação e crescente adesão à criação e utilização de imagens HDR (High Dynamic Range), quer de fotografias do mundo real quer imagens geradas por computador através de software específico, tornase necessário permitir a sua adequada visualização nos dispositivos de visualização convencionais, incluindo os pequenos e limitados, mas amplamente difundidos, dispositivos com ecrã pequeno (DEP) como os Personal Digital Assistants (PDA). Apesar do considerável esforço na melhoria destes dispositivos, as suas limitações continuam a ser notórias, salientando-se o reduzido tamanho, resolução e gama de cores disponíveis. Conforme demonstrámos em experiências anteriores, este tipo de dispositivos necessitam de um operador de mapeamento de tons (Tone Mapping Operator - TMO) adequado que maximize a percepção de imagens HDR. Neste artigo expomos o estado actual do desenvolvimento deste novo TMO para DEP

Tone Reproduction for Interactive Walkthroughs

When a rendering algorithm has created a pixel array of radiance values the task of producing an image is not yet completed. In fact, to visualize the result the radiance values still have to be mapped to luminances, which can be reproduced by the used display. This step is performed with the help of tone reproduction operators. These tools have mainly been applied to still images, but of course they are just as necessary for walkthrough applications, in which several images are created per second. In this paper we illuminate the physiological aspects of tone reproduction for interactive applications. It is shown how tone reproduction can also be introduced into interactive radiosity viewers, where the tone reproduction continuously adjusts to the current view of the user. The overall performance is decreased only moderately, still allowing walkthroughs of large scenes. 1. Introduction Physically based rendering can be split into three phases. First a model of the virtual worl..