Level of Detail (LoD) techniques for real-time... In this paper, we are particularly interested in the problem of realistic collision simulation in scenes where large numbers of objects are colliding and processing must occur in real-time. An interruptible and therefore degradable collision handling mechanism is used and the perceptual impact of this degradation is explored. We look for ways in which we can optimise the realism of such simulations and describe a series of psychophysical experiments that investigated different factors affecting collision perception, including eccentricity, separation, distractors, causality and accuracy of physical response. Finally, strategies for incorporating these factors into a perceptually adaptive real-time simulation of large numbers of visually similar objects are presented.

To reexamine the role of covert attention in visual search, the authors directly manipulated attention by peripherally cueing the target location and analyzed its effects on the set-size and the eccentricity effects. Observers participated in feature and conjunction tasks. Experiment 1 used precues, and Experiment 2 used postcues in a yes-no task under valid-, invalid-, and neutral-cueing conditions. Experiments 3 and 4 used a 2-interval alternative forced-choice visual-search task under cued and neutral conditions. Precueing the target location improved performance in feature and conjunction searches; postcueing did not. For the cued targets, the eccentricity effect for features and conjunctions was diminished, suggesting that the attentional mechanism improves the quality of the sensory representation of the attended location. The conjunction set-size effect was reduced but not eliminated. This questions serial-search models that attribute a major role to covert attention in visual search. Visual search is one of the leading paradigms in the study of visual perception and attention. In a typical visual-search experiment, observers have to decide whether or not a target is present in a visual array containing other nonrelevant items (distractors). For some stimuli, but not for all, reaction time (RT) increases as the number of distractors increases, a phenomenon known as the set-size effect. A large number of studies that attribute this effect to limited covert attentional processes have used the visual-search paradigm to investigate the nature of attention allocation. When performance is not affected by the number of distractors, it is assumed that the array is searched in parallel, preattentively, but a performance that deteriorates as set size increases is interpreted as indicating a covert attentional serial search (e.g.,

This study used peripheral precueing to explore the effect of covert transient attention on performance in spatial resolution tasks. Experiments 1 (Landolt-square) and 2 (‘broken-line’) measured gap resolution and Experiment 3 measured vernier resolution. In all three tasks the target was presented alone in a large number of possible locations, ranging from 1.5–6 ° of eccentricity in the vertical or horizontal axes. The precue indicated the target location but did not convey information regarding the correct response. Performance decreased as the gap size or the vernier offset size decreased and as target eccentricity increased. Precueing improved performance in terms of RT and accuracy in all three tasks; the eccentricity effect decreased in the cued trials of the gap resolution tasks. These findings support the idea that the performance improvement at attended locations results, to some extent, from an enhanced spatial resolution at the cued location, and not just from distractor exclusion, diminished uncertainty, or decisional factors.

This study is the first to investigate: (a) #temporal performance fields,' whether the speed of information accrual di#ers for di#erent locations at a fixed eccentricity, and (b) whether covert attention modulates temporal dynamics di#erentially at isoeccentric locations. Using the speed accuracy tradeo# (SAT) procedure, we derived conjoint measures of how isoeccentric locations and precueing targets location a#ect speed and accuracy in a search task. The results demonstrate the existence of temporal performance fields, analogous to spatial performance fields: information accrual was fastest for target on the horizontal meridian, intermediate for targets at the intercardinal locations, slow for targets on the vertical meridian, and slowest for targets at the North (N) location (accrual time pattern: E&W< intercardinal <S< N). Surprisingly, in contrast to spatial performance fields, where covert attention enhanced discriminability at all locations to a similar degree, attention di#erentially sped up processing at the slower locations, with a greater benefit evident along the vertical than the horizontal meridian, particularly at the N location, and an intermediate benefit at intercardinal locations (viz., N> S> intercardinal >E&W). Hence, the compensatory e#ect of attention eliminated the temporal asymmetries across isoeccentric locations.

The gaze movements accompanying target localization were examined via human observers and a computational model (target acquisition model [TAM]). Search contexts ranged from fully realistic scenes to toys in a crib to Os and Qs, and manipulations included set size, target eccentricity, and target–distractor similarity. Observers and the model always previewed the same targets and searched identical displays. Behavioral and simulated eye movements were analyzed for acquisition accuracy, efficiency, and target guidance. TAM’s behavior generally fell within the behavioral mean’s 95% confidence interval for all measures in each experiment/condition. This agreement suggests that a fixed-parameter model using spatiochromatic filters and a simulated retina, when driven by the correct visual routines, can be a good general-purpose predictor of human target acquisition behavior.

In this chapter, we will discuss the usefulness of eye-tracking for computer applications that attempt to render simulations at interactive rates.

time course of visual competition to the presentation

Saccade target selection in visual search: the effect of information

Explaining human multiple object tracking as

www.elsevier.com/locate/visres Saccade target selection in visual search: the effect of information