A psychophysical investigation of global illumination algorithms used in augmented reality

Global illumination rendering algorithms are capable of producing images that are visually realistic. However, this typically comes at a large computational expense. The overarching goal of this research was to compare different rendering solutions in order to understand why some yield better results when applied to rendering synthetic objects into real photographs. As rendered images are ultimately viewed by human observers, it was logical to use psychophysics to investigate these differences. A psychophysical experiment was conducted judging the composite images for accuracy to the original photograph. In addition, iCAM, an image color appearance model, was used to calculate image differences for the same set of images. In general it was determined that any full global illumination is better than direct illumination solutions only. Also, it was discovered that the full rendering with all of its artifacts is not necessarily an indicator of judged accuracy for the final composite image. Finally, initial results show promise in using iCAM to predict a relationship similar to the psychophysics, which could eventually be used in-the-rendering-loop to achieve photo-realism

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Depolarized Holography with Polarization-multiplexing Metasurface

The evolution of computer-generated holography (CGH) algorithms has prompted significant improvements in the performances of holographic displays. Nonetheless, they start to encounter a limited degree of freedom in CGH optimization and physical constraints stemming from the coherent nature of holograms. To surpass the physical limitations, we consider polarization as a new degree of freedom by utilizing a novel optical platform called metasurface. Polarization-multiplexing metasurfaces enable incoherent-like behavior in holographic displays due to the mutual incoherence of orthogonal polarization states. We leverage this unique characteristic of a metasurface by integrating it into a holographic display and exploiting polarization diversity to bring an additional degree of freedom for CGH algorithms. To minimize the speckle noise while maximizing the image quality, we devise a fully differentiable optimization pipeline by taking into account the metasurface proxy model, thereby jointly optimizing spatial light modulator phase patterns and geometric parameters of metasurface nanostructures. We evaluate the metasurface-enabled depolarized holography through simulations and experiments, demonstrating its ability to reduce speckle noise and enhance image quality.Comment: 15 pages, 13 figures, to be published in SIGGRAPH Asia 202

Situated Displays in Telecommunication

In face to face conversation, numerous cues of attention, eye contact, and gaze direction provide important channels of information. These channels create cues that include turn taking, establish a sense of engagement, and indicate the focus of conversation. However, some subtleties of gaze can be lost in common videoconferencing systems, because the single perspective view of the camera doesn't preserve the spatial characteristics of the face to face situation. In particular, in group conferencing, the `Mona Lisa effect' makes all observers feel that they are looked at when the remote participant looks at the camera. In this thesis, we present designs and evaluations of four novel situated teleconferencing systems, which aim to improve the teleconferencing experience. Firstly, we demonstrate the effectiveness of a spherical video telepresence system in that it allows a single observer at multiple viewpoints to accurately judge where the remote user is placing their gaze. Secondly, we demonstrate the gaze-preserving capability of a cylindrical video telepresence system, but for multiple observers at multiple viewpoints. Thirdly, we demonstrated the further improvement of a random hole autostereoscopic multiview telepresence system in conveying gaze by adding stereoscopic cues. Lastly, we investigate the influence of display type and viewing angle on how people place their trust during avatar-mediated interaction. The results show the spherical avatar telepresence system has the ability to be viewed qualitatively similarly from all angles and demonstrate how trust can be altered depending on how one views the avatar. Together these demonstrations motivate the further study of novel display configurations and suggest parameters for the design of future teleconferencing systems

Proceedings experiencing light 2009 : international conference on the effects of light on welbeing

no abstrac

Proceedings experiencing light 2009 : international conference on the effects of light on welbeing

no abstrac

Factors Affecting Spatial Awareness in Non- Stereo Visual Representations of Virtual, Real and Digital Image Environments

The increasing number of applications employing virtual environment (VE) technologies as a tool, particularly those that use VE as surrogates, makes it important to examine the ability of VE to provide realistic simulations to users. Accurate space and distance perceptions have been suggested as essential preconditions for the reliable use of VE technologies in various applications. However, space and distance perception in the VE has been reported by some investigators as being perceived differently from the real world. Thus, the overall aim of this thesis is to improve our understanding of factors affecting spatial awareness in the VE. The general approach is based on a strategy of conducting empirical investigations comparing tasks performed in the VE to similar tasks performed in the real world. This research has examined the effect of display related factors on users' spatial task performance in the context of static, dynamic and interactive presentations. Three sets of experiments in these respective contexts were conducted to explore the influence of image type, display size, viewing distance, physiological cues, interface device and travel modes on distance estimate and spatial memory tasks. For distance perception, results revealed that the effect of image type depends on the context of presentations, the type of asymmetrical distances and image resolution. The effect of display size in static and dynamic presentations is consistent with the results of previous investigations. However, results from evaluations conducted by the author have indicated that other factors such as viewing distance and physiological cues were also accountable. In interactive presentations, results indicated that display size had different effects on different users whereby familiarity with display size may influence user's performance. Similarly, it was shown that a commonly used interface device is more useful and beneficial for user's spatial memory performance in the VE than the less familiar ones. In terms of travel mode, the natural method of movement available in the real world may not necessary be better than the unnatural movement which is possible in the VE. The results of investigations reported in this thesis contribute towards knowledge and understanding on factors affecting spatial awareness in the real and VE. In particular, they highlight the influence of these factors in space and distance perception in different contexts of VE presentations which will serve as important scientifically based guidelines for designers and users ofVE applications