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Papers by Robert S Allison

The quality of stereoscopic 3D cinematic content is a major determinant for user experience in im... more The quality of stereoscopic 3D cinematic content is a major determinant for user experience in immersive cinema 13 in both traditional theatres and cinematic virtual reality. One of the most important parameters is the frame rate 14 of the content which has historically been 24 frames per second for movies, but higher frame rates are being 15 considered for cinema and are standard for virtual reality. A typical behavioural response to immersive 16 stereoscopic 3D content is vection, the visually-induced perception of self-motion elicited by moving scenes. In 17 this work we investigated how participants' vection varied with simulated virtual camera speed, frame rate, and 18 motion blur produced by the virtual camera's exposure, while viewing depictions of movement through a realistic 19 virtual environment. We also investigated how their postural sway varied with these parameters and how sway 20 covaried with levels of perceived self-motion. Results show that while average perceived vection significantly 21 increased with 3D content frame rate and motion speed, motion blur had no significant effect on perceived 22

Changing head orientation with respect to gravity changes the dynamic sensitivity of the otoliths... more Changing head orientation with respect to gravity changes the dynamic sensitivity of the otoliths to linear accelerations (gravitational and inertial). We explored whether varying head orientation and optic flow direction relative to gravity affects the perception of visually induced self-motion (vection) in two experiments. We confirmed that vertical optic flow produces stronger vection than horizontal optic flow in upright observers. We hypothesized that if this was due to aligning the simulated self-motion with gravity, then interaural (as opposed to spinal) axis motion while lying on the side would provide a similar vection advantage. Alternatively, motion along the spinal axis could enhance vection regardless of head orientation relative to gravity. Finally, we hypothesized that observer expectation and experience with upright locomotion would favour horizontal vection, especially when in upright posture.

Smoothness of stimulus motion can affect vection strength

Experimental brain research, 2018

We examined the effect of the smoothness of motion on vection strength. The smoothness of stimulu... more We examined the effect of the smoothness of motion on vection strength. The smoothness of stimulus motion was modulated by varying the number of frames comprising the movement. In this study, a horizontal grating translated through 360° of phase in 1 s divided into steps of 3, 4, 6, 12, 20, 30, or 60 frames. We hypothesized that smoother motion should induce stronger vection because the smoother stimulus is more natural and contains more motion energy. We examined this effect of frame number on vection for both downward (Experiment 1) and expanding (Experiment 2) optical flow. The results clearly showed that vection strength increased with increasing frame rate, however, the rates of increase in the vection strength with frame rate are not constant, but rapidly increase in the low frame-rate range and appear to asymptote in the high range. The strength estimates saturated at lower frame rates for expanding flow than for downward flow. This might be related to the fact that to proces...

Analysis of the Influence of Vertical Disparities Arising in Toed-in Stereoscopic Cameras

Journal of Imaging Science and Technology

Distortions of Space in Stereoscopic 3D Content

Howard’s Devices

Perception Ecvp Abstract, 2014

Illusory scene shearing during real and illusory self-rotations in roll

Directional data arising from psychophysical studies requires careful processing due to its cycli... more Directional data arising from psychophysical studies requires careful processing due to its cyclical nature. Unlike linear variables such as response time and intensity, directions can be represented as angles or vectors on a circle, may have no natural zero-point or magnitude, and are defined on a periodic circle rather than an infinite line. Because of these unique features, directional data necessitates the use of circular statistical methods; however, unfamiliarity and limited availability of software that support circular data analysis have largely led to its under-use and misapplication. Here the implications of using linear statistics for circular data were explored by submitting data from a behavioural study to both circular and linear statistical analysis.

Proceedings of the 2004 ACM SIGGRAPH international conference on Virtual Reality continuum and its applications in industry - VRCAI '04, 2004

The incorporation of haptic interfaces into collaborative virtual environments is challenging whe... more The incorporation of haptic interfaces into collaborative virtual environments is challenging when the users are geographically distributed. Reduction of latency is essential for maintaining realism, causality and the sense of co-presence in collaborative virtual environments during closely-coupled haptic tasks. In this study we consider the effects of varying amounts of simulated constant delay on the performance of a simple collaborative haptic task. The task was performed with haptic feedback alone or with visual feedback alone. Subjects were required to make a coordinated movement of their haptic displays as rapidly as possible, while maintaining a target simulated spring force between their end effector and that of their collaborator. Increasing simulated delay resulted in a decrease in performance, either in deviation from target spring force and in increased time to complete the task. At large latencies, there was evidence of dissociation between the states of the system that was observed by each of the collaborating users. This confirms earlier anecdotal evidence that users can be essentially seeing qualitatively different simulations with typical long distance network delays.

In modern Night Vision Devices (NVDs) halo around bright light sources remains a salient imaging ... more In modern Night Vision Devices (NVDs) halo around bright light sources remains a salient imaging artifact. Although a common feature of image intensified imagery, little is known of the perceptual and operational effects of this device limitation. This paper describes two related sets of experiments. In the first set of experiments, we provide quantitative measurements of Night Vision Device (NVD) halos formed by light sources as a function of intensity and distance. This characterization allows for analysis of the possible effects of halo on human perception through NVDs. In the second set of experiments, the effects of halation on the perception of depth and environmental layout are investigated psychophysically. The custom simulation environment used and results from psychophysical experiments designed to analyze halo-induced errors in slope estimation are presented.

Effect of disparity noise on sterescopic surface perception in human and ideal observers

Display Technology Journal of, Apr 1, 2012

The hypothesis that artefacts related to chromatic aberration from eyeglasses may be more objecti... more The hypothesis that artefacts related to chromatic aberration from eyeglasses may be more objectionable in laser projectors compared to conventional digital projectors was investigated. Untrained observers viewed movie clips in a theater and made image quality ratings. The same four clips were presented on both a standard Xenon display and a prototype laser projector in separate blocks. There was no evidence that observers noticed color break-up artefacts using either mode of presentation.

Proceedings of the Workshop on Virtual Environments 2003, May 22, 2003

Six-sided fully immersive projective displays present complex and novel problems for tracking sys... more Six-sided fully immersive projective displays present complex and novel problems for tracking systems. Existing tracking technologies typically require tracking equipment that is placed in locations or attached to the user in a way that is suitable for typical displays of five or less walls but which would interfere with the immersive experience within a fully enclosed display. This paper presents a novel vision-based tracking technology for fully-immersive projective displays. The technology relies on the operator wearing a set of laser diodes arranged in a specific configuration and then visually tracking the projection of these lasers on the external walls of the display outside of the user's view. This approach places minimal hardware on the user and no visible tracking equipment is placed within the immersive environment. This paper describes the basic visual tracking system including the hardware and software infrastructure.

Binocular slant discrimination beyond interaction space

J Vision, 2010

F1000posters, Sep 13, 2011

The geometry of stereopsis makes straightforward predictions regarding the effect of increasing a... more The geometry of stereopsis makes straightforward predictions regarding the effect of increasing an observer's simulated interocular distance, which can be simulated by changing the stereo cameras interaxial distance (IA), on perceived depth. Our aim is to characterize the effect of IA on perceived depth, and its dependence on scene complexity and screen size. The presence of multiple realistic depth cues has significant and complex effects on perceived depth from binocular disparity; effects that are not obvious from binocular geometry.

The Camera Convergence Problem Revisited

Proceedings of Spie the International Society For Optical Engineering, May 1, 2004

The camera convergence problem revisited. [Proceedings of SPIE 5291, 167 (2004)]. Robert S. Allis... more The camera convergence problem revisited. [Proceedings of SPIE 5291, 167 (2004)]. Robert S. Allison. Abstract. Convergence of the real or virtual stereoscopic cameras is an important operation in stereoscopic display systems. ...

Temporal Dependencies In Resolving

In order to measure the perceived direction of "up", subjects judged the three-dimensional shape ... more In order to measure the perceived direction of "up", subjects judged the three-dimensional shape of disks shaded to be compatible with illumination from particular directions. By finding which shaded disk appeared most convex, we were able to infer the perceived direction of illumination. This provides an indirect measure of the subject's perception of the direction of "up". The different cues contributing to this percept were separated by varying the orientation of the subject and the orientation of the visual background relative to gravity. We also measured the effect of decreasing or increasing gravity by making these shape judgements throughout all the phases of parabolic flight (0g, 2g and 1g during level flight). The perceived up direction was modeled by a simple vector sum of "up" defined by vision, the body and gravity. In this model, the weighting of the visual cue became negligible under microgravity and hypergravity conditions.

Sensitivity to monocular occlusions in stereoscopic imagery: Implications for S3D content creation, distribution and exhibition