Robert J. Beaton

Evaluating natural interaction techniques in video games

Despite the gaming industrys recent trend for using “natural” interaction techniques, which mimic real world actions with a high level of fidelity, it is not clear how natural interaction techniques affect the player experience. In order to obtain a better understanding, we designed and conducted a study using Mario Kart Wii, a commercial racing game for the Nintendo Wii. We chose this platform due to its seemingly balanced design of both natural and non-natural interaction techniques. Our empirical study of these techniques found that the non-natural interaction techniques significantly outperform their more natural counterparts. We offer three hypotheses to explain our finding and suggest them as important interaction design considerations.

Considerations for the use of commercial video games in controlled experiments

While commercial, off-the-shelf video games have been used often to observe cognitive and social phenomena, few studies have taken advantage of such games as research tools for conducting controlled experiments. Providing evidence that unmodified, commercial video games can be used to conduct gaming evaluations with high levels of both experimental control and ecological validity, we designed and conducted an experiment that utilized Mario Kart Wii to evaluate the effects of natural interaction on player performance. Based on our experience from that experiment, we present several concerns that require attention when using commercial video games as research tools. Providing examples of design decisions and outcomes from our experiment, we identify some of the benefits, drawbacks, and challenges of using such tools.

Comparison of depth cues for relative depth judgments

This paper reports on two experiments in which subjects judged the relative depth ordering and subjective quality of depth of simple, geometric figures (planar circle, square, and triangle). The 3-D images were presented on a Tektronix SGS 620 field-sequential stereoscopic CRT. Four sources of depth information (cue types) were combined factorially to construct exemplary 3-D images: Relative Size (angular subtense decreased with increasing depth); Disparity (binocular disparity varied from crossed to uncrossed with increasing depth); Interposition (closer figures overlapped ones farther away in depth); and Luminance (luminance decreased with increasing depth). Inclusion of each of the three monocular cues produced significantly faster depth judgments. However, there was a lack of significant response time effects associated with binocular disparity. Conversely, stereo presentations strongly improved ratings of subjective image quality. These data indicate that stereoscopic images may provide subjectively more compelling depth information than images containing only monocular cues. However, they also provide evidence for at least one limitation of stereoscopic display utility.

Quantitative Models of Image Quality

Fourteen image quality metrics were evaluated for hard-copy and soft-copy displays of digital images degraded by various levels of noise and blur. All quality metrics were formulated to include the displayed modulation spectrum of the image. The statistical analyses suggested that several of the metrics correlated strongly with performance, and, thus, support the proposed utility of image-dependent quality measures. An MTFA-type metric was shown to correlate highest with the average performance scores across noise and blur conditions.

Some effects on depth-position and course-prediction judgments in 2-D and 3-D displays

With increasing use of three-dimensional stereoscopic display systems, there is a need to define optimal user interface guidelines for these systems. This study examines human performance in two tasks which required participants to view 3-D imagery with or without retinal disparity cues. The imagery consisted of an airspace control zone and it was rendered on the display screen in each of three formats: (1) a plan view, (2) a simple perspective view, and (3) an enhanced perspective view. One task required viewers to judge relative depth positions for objects within the 3-D space, while the other task required extrapolation of object motion headings. Retinal disparity cues reduced both the number and degree of errors, but only for the plan view, course prediction task condition. Not only did retinal disparity cues not provide any performance advantages for perspective displays, but performance levels for these displays were no different than those achievable with a plan view in the absence of retinal disparity cues. Although retinal disparity cues had no effect on search time, the enhanced perspective displays formats effectively increased search times relative to plan view and simple perspective formats. Neither retinal disparity cues nor display format had an effect on subjective ratings of viewer confidence.

An Evaluation of System Quality Metrics for Hard-Copy and Soft-Copy Displays of Digital Imagery

This paper reports an evaluation of 16 quantitative models of system quality for hard-copy (i.e., positive film transparencies) and soft-copy (i.e., CRT-based) displays of digitally derived imagery. The results demonstrate that the effects of system noise and blur degradation upon photointerpretation and subjective scaling performance can be predicted, on an a priori basis, with better than 85% accuracy.

Design of a spatial-chromatic human vision model for evaluating full-color display systems

Two general characteristics of full-color display systems which are known to impact image quality include the ability of the display system to transfer modulation (chromatic as well as achromatic) and the degree to which the display system adds noise (chromatic and achromatic) to the signal. This paper describes a model of human spatial-chromatic vision and a corresponding procedure for using the model to evaluate color display systems. Together the proposed model and procedure constitute a color image quality metric which is responsive to the modulation transfer and noise generating characteristics of a display system. The proposed human vision model employs processing stages which simulate blurring by the optics of the eye, linear spectral absorption by three classes of cone, addition of internal noise, nonlinear transduction by retinal mechanisms, derivation of opponent-color images, and calculation of the responses of linear spatial mechanisms with finite spatial frequency and orientation bandwidth. A summary of the modulation detection, discrimination, and suprathreshold contrast perception performance of the model is presented and compared with human performance data from the visual science literature. A procedure for evaluating display systems using the model is described and the results of several analyses of display systems are presented. High correlations between predictions made by the model and the results of image quality studies from the display design literature have been obtained with no free parameters in the model. The results of the validation studies conducted so far suggest that the proposed method for evaluating color display systems is viable and warrants critical examination.

Human Performance Evaluations Of Digital Image Quality

This paper reports some of the findings of a research program aimed at investigating the effects of digital image quality upon human performance. Two image quality dimensions, blur and noise, along with three display systems were studied by employing two human performance tasks. The results, in conjunction with the evaluation of enhancement/restoration techniques provide useful information for digital imaging system and subsystem designers.

Image Interpretation for Soft-Copy Displays of Digitally Derived Images

The effects of manipulating image noise and image blur were determined on an information extraction task using soft-copy displays. The participants in this study were 15 military photointerpreters from Langley Air Force Base, Virginia. The empirical findings indicated that the main effect of image noise was statistically significant (p < 0.002) as was the main effect of image blur (p = 0.060). The noise by blur interaction was not statistically significant (p = .872). In general, image interpretation performance decreased with increasing image noise and image blur levels. This pattern of results was very similar to the empirical observations of a previous study which employed the same image and task conditions for hard-copy displays.

Evaluation of CRT-Displayed Digital Imagery Using Subjective Scaling

Rapid technological transition from analog images to digital images has necessitated the development of a research program for evaluating digital image quality. This paper investigated the perceived interpretability of static, digitized monochrome images displayed on CRTs. Quality judgments of two image degradations: blur and noise, were evaluated by a subjective scaling technique. The digital images consisted of 10 scenes, each of which was degraded by 5 levels of blur and 5 levels of noise, yielding a set of 250 images. Fifteen Air Force photointerpreters participated in the study. The photointerpreters viewed the images on CRTs and rated the interpretability of each image on a 10-point NATO scale. Analysis of the scaling values indicated that the blur, noise, and interaction effects were statistically significant. Perceived interpretability of the images decreased monotonically as the physical image degradation increased. In a separate study, the photointerpreters extracted information from a selected subset of images. Correlation between the scaling values and the actual information extracted was high. This result suggests that information extraction performance can be accurately predicted from subjective quality judgments. Comparisons between CRT-displayed imagery with film-based digital imagery showed no differences. Subjective quality judgments were similar for the two display formats.