Mikko Kytö

Method for measuring stereo camera depth accuracy based on stereoscopic vision

We present a method to evaluate stereo camera depth accuracy in human centered applications. It enables the comparison between stereo camera depth resolution and human depth resolution. Our method uses a multilevel test target which can be easily assembled and used in various studies. Binocular disparity enables humans to perceive relative depths accurately, making a multilevel test target applicable for evaluating the stereo camera depth accuracy when the accuracy requirements come from stereoscopic vision. The method for measuring stereo camera depth accuracy was validated with a stereo camera built of two SLRs (singlelens reflex). The depth resolution of the SLRs was better than normal stereo acuity at all measured distances ranging from 0.7 m to 5.8 m. The method was used to evaluate the accuracy of a lower quality stereo camera. Two parameters, focal length and baseline, were varied. Focal length had a larger effect on stereo cameras depth accuracy than baseline. The tests showed that normal stereo acuity was achieved only using a tele lens. However, a users depth resolution in a video see-through system differs from direct naked eye viewing. The same test target was used to evaluate this by mixing the levels of the test target randomly and asking users to sort the levels according to their depth. The comparison between stereo camera depth resolution and perceived depth resolution was done by calculating maximum erroneous classification of levels.

Improving relative depth judgments in augmented reality with auxiliary augmentations

Significant depth judgment errors are common in augmented reality. This study presents a visualization approach for improving relative depth judgments in augmented reality. The approach uses auxiliary augmented objects in addition to the main augmentation to support ordinal and interval depth judgment tasks. The auxiliary augmentations are positioned spatially near real-world objects, and the location of the main augmentation can be deduced based on the relative depth cues between the augmented objects. In the experimental part, the visualization approach was tested in the “X-ray” visualization case with a video see-through system. Two relative depth cues, in addition to motion parallax, were used between graphical objects: relative size and binocular disparity. The results show that the presence of auxiliary objects significantly reduced errors in depth judgment. Errors in judging the ordinal location with respect to a wall (front, at, or behind) and judging depth intervals were reduced. In addition to reduced errors, the presence of auxiliary augmentation increased the confidence in depth judgments, and it was subjectively preferred. The visualization approach did not have an effect on the viewing time.

Stereoscopic depth perception in video see-through augmented reality within action space

Abstract. Depth perception is an important component of many augmented reality applications. It is, however, subject to multiple error sources. In this study, we investigated depth judgments with a stereoscopic video see-through head-mounted display for the purpose of designing depth cueing for systems that operate in an individual’s action space. In the experiment, we studied the use of binocular disparity and relative size to improve relative depth judgments of augmented objects above the ground plane. The relative size cue was created by adding auxiliary augmentations to the scene according to constraints described in the section on the underlying theory. The results showed that binocular disparity and relative size improved depth judgments over the distance range. This indicates that for accurate depth judgments, additional depth cues should be used to facilitate stereoscopic perception within an individual’s action space.

Effect of camera separation on the viewing experience of stereoscopic photographs

This study presents a geometric and subjective analysis of typical mobile stereoscopic 3-D images. The geometry of the stereoscopic pipeline from the scene to the eyes of the viewer is a highly relevant issue in stereoscopic media. One important factor is camera separation, because it can be used to control the perceived depth of stereoscopic images. The geometric analysis included consideration of disparity and roundness factor within typical mobile stereoscopic imaging scenes. These geometric properties of stereoscopic 3-D images were compared to subjective evaluations by varying camera separation in different scenes. The participants in this study evaluated the strength and naturalness of depth sensation and the overall viewing experience from still images with the single-stimulus method. The results showed that participants were able to perceive the change of depth range even though the images were shown in random order without a reference depth scale. The highest naturalness of depth sensation and viewing experience were achieved with 2 cm to 6 cm camera separation in every content. With these preferred camera separations, the disparity range was less than ±1 deg⁡ and cardboard effect (quantified with roundness factor) did not negatively affect the naturalness of depth sensation.

Exploring Seasonality in Mobile Cultural Heritage

We present results of an investigation into the role of seasonality in mobile cultural heritage applications. 45 participants in 26 groups used one of two applications when visiting the Finnish recreational island of Seurasaari. Each provided summer and winter content, but varied in how this was presented. We uncovered how users consider seasonality in content, seasonal preferences, as well as how different media becomes more or less interesting if shown in or out of season. We present design considerations for future researchers to consider seasonality in cultural heritage applications.

Investigating user generated presentations of self in face-to-face interaction between strangers

Abstract A recent trend in HCI has been the reuse of social media to augment face-to-face interactions amongst strangers. Where Digital presentation of media are displayed during face-to-face encounters. Work has shown that displaying media when co-present with a stranger can help to support conversation. However, existing work considers social media as a raw resource, using algorithmic matching to identify shared topics between individuals, presenting these as text. Therefore, we do not know how users would choose digital media to represent themselves to others or how they would wish it to be displayed. This is important, as existing work fails to take into account the rich practices around how users choose to represent themselves on-line to others, and the implications if unwanted data are disclosed. Through a two-part study 32 participants designed a digital representation of themselves that could be presented to strangers in face-to-face interaction. We then studied how these were employed. Our results found that users prefer more social, rich and ambiguous content to present, the majority of which comes from outside existing social and digital media services. The use of ambiguous content helping to both sustain conversation, and being used as a way to control disclosure of information. By considering two display technologies (HMD and Smartwatch) we are also able to decouple the role of the visualisation from how it is displayed, identifying how showing the visualisation can help in the conversation.

Improving 3D Character Posing with a Gestural Interface

The most time-consuming part of character animation is 3D character posing. Posing using a mouse is a slow and tedious task that involves sequences of selecting on-screen control handles and manipulating the handles to adjust character parameters, such as joint rotations and end effector positions. Thus, various 3D user interfaces have been proposed to make animating easier, but they typically provide less accuracy. The proposed interface combines a mouse with the Leap Motion device to provide 3D input. A usability study showed that users preferred the Leap Motion over a mouse as a 3D gestural input device. The Leap Motion drastically decreased the number of required operations and the task completion time, especially for novice users.

Pinpointing: Precise Head- and Eye-Based Target Selection for Augmented Reality

Head and eye movement can be leveraged to improve the users interaction repertoire for wearable displays. Head movements are deliberate and accurate, and provide the current state-of-the-art pointing technique. Eye gaze can potentially be faster and more ergonomic, but suffers from low accuracy due to calibration errors and drift of wearable eye-tracking sensors. This work investigates precise, multimodal selection techniques using head motion and eye gaze. A comparison of speed and pointing accuracy reveals the relative merits of each method, including the achievable target size for robust selection. We demonstrate and discuss example applications for augmented reality, including compact menus with deep structure, and a proof-of-concept method for on-line correction of calibration drift.

Tangible Interaction for Stroke Survivors: Design Recommendations

In this paper we outline the initial stages of a human centered design process aimed at the design of novel technology (tangible interactive objects) for stroke survivors. We found it useful to support standard methods, such as interviews and focus groups, with a video prototype in order to make the concept of tangible interaction, which was novel to our users, more clear. In addition we carried out a co-design workshop together with stroke survivors. Based on these activities, we present a set of preliminary design guidelines for tangible interaction for stroke survivors.

Augmenting Multi-Party Face-to-Face Interactions Amongst Strangers with User Generated Content

We present the results of an investigation into the role of curated representations of self, which we term Digital Selfs, in augmented multi-party face-to-face interactions. Advancements in wearable technologies (such as Head-Mounted Displays) have renewed interest in augmenting face-to-face interaction with digital content. However, existing work focuses on algorithmic matching between users, based on data-mining shared interests from individuals’ social media accounts, which can cause information that might be inappropriate or irrelevant to be disclosed to others. An alternative approach is to allow users to manually curate the digital augmentation they wish to present to others, allowing users to present those aspects of self that are most important to them and avoid undesired disclosure. Through interviews, video analysis, questionnaires and device logging, of 23 participants in 6 multi-party gatherings where individuals were allowed to freely mix, we identified how users created Digital Selfs from media largely outside existing social media accounts, and how Digital Selfs presented through HMDs were employed in multi-party interactions, playing key roles in facilitating strangers to interact with each other. We present guidance for the design of future multi-party digital augmentations in collaborative scenarios.