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symposium on applied perception in graphics and visualization

作者： Yoshida, Akiko Ihrke, Matthias Mantiuk, Rafal Seidel, Hans-Peter Univ British Columbia MPI Informat Vancouver BC V5Z 1M9 Canada BCCN Gottingen Gottingen Germany

ISBN: (纸本)9781595939814

The glare illusion is commonly used in CG rendering, especially in game engines, to achieve a higher brightness than that of the maximum luminance of a display. In this work, we measure the perceived luminance of the glare illusion in a psychophysical experiment. To evoke the illusion, an image is convolved with either a point spread function (PSF) of the eye or a Gaussian kernel. It is found that 1) the Gaussian kernel evokes an illusion of the same or higher strength than that produced by the PSF while being computationally much less expensive, 2) the glare illusion can raise the perceived luminance by 20 - 35%, 3) some convolution kernels can produce undesirable Mach-band effects and thereby reduce the brightness boost of the glare illusion. The reported results have practical implications for glare rendering in computer graphics.

关键词： Glare illusion Human Visual Systems (HVS) Psychophysics

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Frequency Analysis to Facilitate the Recognition of Images 08

Frequency Analysis to Facilitate the Recognition of Images

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symposium on applied perception in graphics and visualization

作者： He, Yin Yan, Xin Bartram, Lyn Simon Fraser Univ Sch Interact Arts & Technol Burnaby BC V5A 1S6 Canada

ISBN: (纸本)9781595939814

Content based image retrieval is an approach for facilitating the searching and browsing of large image collections. In this approach, image analysis is conducted on low level visual properties extracted from the image. We believed that in order to create an effective image retrieval system, visual perception must be taken into account. We conjectured that a technique which employs both M and P pathways would be more effective in the discrimination and search tasks of thumbnails. While the P pathway representations are easy to judge by observing color and shape, assessment of M pathway is possible through spatial frequency filtering. In order to validate this claim, a study was conducted to look at how manipulating spatial frequency composition of thumbnails affects visual search time. Thumbnails were sorted using frequency analysis and a user study measured recognition time, correctness of response, and number of repeated trials.

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Comprehending Boolean Queries 08

Comprehending Boolean Queries

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symposium on applied perception in graphics and visualization

作者： Huo, Jiwen Cowan, Win Univ Waterloo David R Cheriton Sch Comp Sci Waterloo ON N2L 3G1 Canada

ISBN: (纸本)9781595939814

Data selection is an integral part of information visualization. It almost universally incorporates Boolean logic in some way, despite the known difficulties of Boolean concepts for users. As a result many different visual interfaces have been proposed for specifying or displaying Boolean queries. In general they are tested experimentally, and though the results are usually promising, they normally show only that one interface is better or worse than another, but not why this is so. This paper describes a new experimental methodology for evaluating query interfaces, which uses stimulus onset asynchrony to separate different aspects of query comprehension. We used it to evaluate a new visual query interface based on Karnaugh maps and discovered that there are two qualitatively different approaches to comprehension, deductive and inductive. The Karnaugh map representation scales extremely well with query complexity, and the experiments show that its good scaling properties occur because it strongly facilitates inductive comprehension.

关键词： visualization stimulus onset asynchrony Boolean query evaluation visual query

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Navigation Modes in Virtual Environments: Walking vs. Joystick 08

Navigation Modes in Virtual Environments: Walking vs. Joysti...

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symposium on applied perception in graphics and visualization

作者： Peng, Peng Riecke, Bernhard E. Williams, Betsy McNamara, Timothy P. Bodenheimer, Bobby Vanderbilt Univ Nashville TN 37203 USA Simon Fraser Univ Burnaby BC V5A 1S6 Canada Rhodes Coll Memphis TN 38112 USA

ISBN: (纸本)9781595939814

There is considerable evidence that people have difficulty maintaining orientation in virtual environments. This difficulty is usually attributed to poor idiothetic cues, such as the absence of proprioception and other sources of information provided by self locomotion. The lack of proprioceptive cues presents a strong argument against the use of a joystick interface, and the importance of full physical movement for navigation tasks has also recently been confirmed by Ruddle and Lessels [2006], who showed that subjects performing a navigational task were superior when they were allowed to walk freely rather than when they could only physically rotate themselves or only move virtually. Our study seeks to confirm the results of Ruddle and Lessels.

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The perceptual influences on gait transition of step parameters and optic flow in virtual environment locomotion simulators 08

The perceptual influences on gait transition of step paramet...

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symposium on applied perception in graphics and visualization

作者： Dong, Huan Pelah, Adar Cameron, Jonathan Lasenby, Joan Univ Cambridge Cambridge CB2 1TN England

ISBN: (纸本)9781595939814

Simulation of natural locomotion in virtual environments requires an understanding of self-motion perception derived from both gait and sensory parameters. The walk-run transition (WRT) is a clearly-defined physical gait descriptor that emerges largely from a user's assessment of their own speed. The WRT depends not only on the biomechanics, kinetics and energetics of gait, but also on perceptual and cognitive factors, such as optic flow [Mohler et al. 2004;2007], attention [Pelah et al 2006] and step frequency [Durgin et al 2007]. To further investigate gait transitions and the mechanisms for perception of self motion speed, 15 subjects were required to advance at prescribed step frequencies with increasing speeds on a treadmill, with or without optic flow, in a large-screen virtual environment. WRT speed reached its highest value at approximately 145 steps/min (0.61 Fr) for all conditions, decreasing at higher step frequencies. Above this frequency, optic flow reduced WRT speeds as step frequency increased, suggesting an enhancement of visuomotor interactions in locomotion simulators due to step frequency being forced beyond the natural step frequency range.

关键词： Locomotion gait step frequency perception optic flow walk-run transition virtual environments

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A Psychophysical study of Fixation Behavior in a Computer Game 08

A Psychophysical Study of Fixation Behavior in a Computer Ga...

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symposium on applied perception in graphics and visualization

作者： Sundstedt, Veronica stavrakis, Efstathios Wimmer, Michael Reinhard, Erik Univ Bristol Bristol BS8 1TH Avon England REVES INRIA Le Chesnay France Vienna Univ Technol Vienna Austria

ISBN: (纸本)9781595939814

Prediction of gaze behavior in gaming environments can be a tremendously useful asset to game designers, enabling them to improve gameplay, selectively increase visual fidelity, and optimize the distribution of computing resources. The use of saliency maps is currently being advocated as the method of choice for predicting visual attention, crucially under the assumption that no specific task is present. This is achieved by analyzing images for low-level features such as motion, contrast, luminance, etc. However, the majority of computer games are designed to be easily understood and pose a task readily apparent to most players. Our psychophysical experiment shows that in a task-oriented context such as gaming, the predictive power of saliency maps at design time can be weak. Thus, we argue that a more involved protocol utilizing eye tracking, as part of the computer game design cycle, can be sufficiently robust to succeed in predicting fixation behavior of players.

关键词： Psychophysics Electronic Games Eye Tracking Visual Attention Eye Movements Saliency

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Misperceptions in stereoscopic Displays: A Vision Science Perspective 08

Misperceptions in Stereoscopic Displays: A Vision Science Pe...

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symposium on applied perception in graphics and visualization

作者： Held, Robert T. Banks, Martin S. Univ Calif Berkeley Berkeley CA 94720 USA

ISBN: (纸本)9781595939814

3d shape and scene layout are often misperceived when viewing stereoscopic displays. For example, viewing from the wrong distance alters an object's perceived size and shape. It is crucial to understand the causes of such misperceptions so one can determine the best approaches for minimizing them. The standard model of misperception is geometric. The retinal images are calculated by projecting from the stereo images to the viewer's eyes. Rays are back-projected from corresponding retinal-image points into space and the ray intersections are determined. The intersections yield the coordinates of the predicted percept. We develop the mathematics of this model. In many cases its predictions are close to what viewers perceive. There are three important cases, however, in which the model fails: 1) when the viewer's head is rotated about a vertical axis relative to the stereo display (yaw rotation);2) when the head is rotated about a forward axis (roll rotation);3) when there is a mismatch between the camera convergence and the way in which the stereo images are displayed. In these cases, most rays from corresponding retinal-image points do not intersect, so the standard model cannot provide an estimate for the 3d percept. Nonetheless, viewers in these situations have coherent 3d percepts, so the visual system must use another method to estimate 3d structure. We show that the non-intersecting rays generate vertical disparities in the retinal images that do not arise otherwise. Findings in vision science show that such disparities are crucial signals in the visual system's interpretation of stereo images. We show that a model that incorporates vertical disparities predicts the percepts associated with improper viewing of stereoscopic displays. Improving the model of misperceptions will aid the design and presentation of 3d displays.

关键词： Depth perception Virtual Reality 3D displays visualization

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Convolution and variational implicit surfaces in sketch-based modeling

Convolution and variational implicit surfaces in sketch-base...

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2007 IADIS International Conference on Computer graphics and visualization, CGV 2007, part of the 1st IADIS Multi Conference on Computer Science and Information Systems, MCCSIS 2007

作者： Kúkelová, Zuzana Ďurikovič, Roman Center for Machine Perception Department of Cybernetics Faculty of Electrical Engineering Czech Technical University Prague Czech Republic Faculty of Natural Sciences University of Saint Cyril and Metod Trnava Slovakia Nam. J. Herdu 2 Trnava917 01 Slovakia Faculty of Mathematics Physics and Informatics Comenius University Mlynska dolina Bratislava842 48 Slovakia

ISBN: (纸本)9789728924393

In this work we focus on function representation suitable for creating 3D freeform shapes with sketched silhouette curves. We aim at comparison of two approaches for sketch-based modeling, namely the skeleton-based convolution surfaces and variational implicit surfaces. Both methods are extended to handle smooth set theoretic operations between components defined by sketching silhouette curves on different projection planes. Our approach includes additional extensions to sketch-based systems like automatic skeleton generation that can be directly used for object animation, carving operation, creating surfaces with handles and surface texturing. © 2007 IADIS.

关键词： Convolution

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The effect of warm and cool object colors on depth ordering 06

The effect of warm and cool object colors on depth ordering

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3rd symposium on applied perception in graphics and visualization, APGV 2006

作者： Bailey, Reynold Grimm, Cindy Davoli, Christopher Washington University St. Louis United States

No abstract available

ISBN: (纸本)1595934294

No abstract available

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Rendering complex scenes for psychophysics using RADIANCE: How accurate can you get?

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JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION 2006年第4期23卷 759-768页

作者： Ruppertsberg, AI Bloj, M Univ Bradford Dept Optometry Bradford BD7 1DP W Yorkshire England

Rendering packages are used by visual psychophysicists to produce complex stimuli for their experiments, tacitly assuming that the simulation results accurately reflect the light-surface interactions of a real scene. RADIANCE is a physically based, freely available, and commonly used rendering software. We validated the calculation accuracy of this package by comparing simulation results with measurements from real scenes. RADIANCE recovers color gradients well but the results are shifted in color space. Currently, there is no better simulation alternative for achieving physical accuracy than by combining a spectral rendering method with RADIANCE. (c) 2006 Optical Society of America.

关键词： BINOCULARLY VIEWED SCENES SURFACE COLOR-perception GLOBAL ILLUMINATION CONstANCY REPRODUCTION SIMULATIONS VALIDATION SHAPE

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