The effect of varying path properties in path steering tasks

Path steering is a primitive 3D interaction task that requires the user to navigate through a path of a given length and width. In a previous paper, we have conducted controlled experiments in which users operated a pen input device to steer a cursor through a 3D path subject to fixed path properties, such as path length, width, curvature and orientation. From the experimental data we have derived a model which describes the efficiency of the task. In this paper, we focus on studying the movement velocity of 3D manipulation path steering when one or more path properties vary during the task. We have performed a repeated measures design experiment of 8 scenarios, including a scenario in which all path properties were kept constant, 3 scenarios in which the path width, curvature and orientation varied, 3 scenarios of varying two path properties, and 1 scenario of varying all properties. The analysis of our experimental data indicates that a path of varying orientation or width results in a low average steering velocity. During a continuous steering, the joint where a change in path curvature or orientation takes place also significantly decreases the velocity. In addition, path width and curvature are highly-correlated to the average velocity of a segment, i.e. the wider a segment (or the smaller the path curvature), the larger the average steering velocity on that segment. The results of this work could serve as guidelines for designing higher level interaction techniques and better user interfaces for traditional HCI tasks, e.g. 2D or 3D nested-menu navigation

First-person locomotion in 3D virtual environments: a usability analysis

3D Virtual Environments (VE) are becoming popular as a tool for cognitive, functional and psychological assessment. Navigation in these environments is recognized as one of the most difficult activities in 3D Virtual Environments (VE). Users unfamiliar to 3D games, specially elder persons, get puzzled when they try to virtually move an avatar through these environments. Their inability to navigate prevents them from concentrating in the task and even to finish it. In this paper, we analyze the influence of different factors in locomotion control. We investigate the impact of having the cursor fixed at the camera center or leaving it free inside the current view. We also analyze the influence of the pitch angle on the camera control. In addition, we have designed an automatic locomotion system that we compare to user-controlled locomotion. We describe a virtual scenario and a test task that we have implemented to evaluate these different methods with users of diverse profiles.Postprint (published version

Revisiting Path Steering for 3D Manipulation Tasks

Thelawof pathsteering,as proposed byAccotandZhai,describes a quantitative relationship between human temporal performance and the path’s spatial characteristics. The steering law is formulatedasacontinuous goalcrossingtask,inwhichalargenumberof goalsarecrossedalongthepath. Thesteeringlawhasbeenverified empirically for locomotion, in which a virtual driving task through straight andcircular paths was performed. Werevisitthepathsteeringlawformanipulationtasksindesktop virtualenvironments. Wehaveconductedcontrolledexperimentsin whichusersoperateapeninputdevicetosteeravirtualballthrough paths of varying length, width, curvature and orientation. Our results indicate that, although the steering law provides a good description of overall task time as a function of index of difficulty ID = L/W, where L and W are the path length and width, it does notaccountforotherrelevantfactors. Wespecificallyshowthatthe influence of curvature can be modeled by a percentage increase in steering time, independent of index of difficulty. The path orientation relative to the viewing direction has a more complex effect on the steering law, which is moreover for instance asymmetric, i.e. it differs whenmoving tothe leftor right. A detailed analysis of our results indicates that a 3D steering movement can probably not be modeled as a sequence of individual goal crossing subtasks. Rather, we can postulate that the overall steering task is likely better described as a sequence of smaller movements that are closer to ballistic movements. One argument for this is that we established that the time for subtrials with continuous steering is related to ID by a power law, with an exponent inthe range 0.5-0.6, rather than being equal to 1as required by the steeringlaw

DEVELOPMENT AND VALIDATION OF SIMULATORS FOR POWER WHEELCHAIR DRIVING EVALUATIONS

Of all those people with severe physical and cognitive disabilities who are rated as unsafe to drive a power wheelchair and hence denied a wheelchair, a significant number can have positive outcomes by using advanced control interfaces and by getting adequate amount of driving training. This dissertation research presents development and user evaluations with a virtual reality based wheelchair driving simulator system. Using the software systems validated in these research studies clinicians can select and customize joystick interfaces that can optimally use their client’s physical and cognitive capabilities. When people with traumatic brain injury and cerebral palsy used the isometric joystick they committed equivalent or lesser driving errors than when they used the conventional movement sensing joystick to drive a wheelchair. Potential wheelchair users can benefit from such customizable control interfaces to reliably and safely control their power wheelchairs and improve their community participation. An immersive virtual reality simulator was further developed as a driving training and evaluation tool. People with various disabilities completed a clinically validated driving evaluation protocol in real and virtual environments. Their virtual driving performances in the simulator were predictive of their performances in real world. Experienced clinicians showed high inter and intra rater reliabilities in their driving evaluations. Research was also performed to understand the relative contribution of different system components of the simulator system to the overall mental and physical workload of users. This research may assist researchers in selecting simulator system components that best suit the clinical needs of potential users. Clinicians who were trained to evaluate wheelchair driving using this system and wheelchair users who used it gave a general positive feedback that that this simulator has good potential for use in clinical or community settings

Low Latency Rendering with Dataflow Architectures

The research presented in this thesis concerns latency in VR and synthetic environments. Latency is the end-to-end delay experienced by the user of an interactive computer system, between their physical actions and the perceived response to these actions. Latency is a product of the various processing, transport and buffering delays present in any current computer system. For many computer mediated applications, latency can be distracting, but it is not critical to the utility of the application. Synthetic environments on the other hand attempt to facilitate direct interaction with a digitised world. Direct interaction here implies the formation of a sensorimotor loop between the user and the digitised world - that is, the user makes predictions about how their actions affect the world, and see these predictions realised. By facilitating the formation of the this loop, the synthetic environment allows users to directly sense the digitised world, rather than the interface, and induce perceptions, such as that of the digital world existing as a distinct physical place. This has many applications for knowledge transfer and efficient interaction through the use of enhanced communication cues. The complication is, the formation of the sensorimotor loop that underpins this is highly dependent on the fidelity of the virtual stimuli, including latency. The main research questions we ask are how can the characteristics of dataflow computing be leveraged to improve the temporal fidelity of the visual stimuli, and what implications does this have on other aspects of the fidelity. Secondarily, we ask what effects latency itself has on user interaction. We test the effects of latency on physical interaction at levels previously hypothesized but unexplored. We also test for a previously unconsidered effect of latency on higher level cognitive functions. To do this, we create prototype image generators for interactive systems and virtual reality, using dataflow computing platforms. We integrate these into real interactive systems to gain practical experience of how the real perceptible benefits of alternative rendering approaches, but also what implications are when they are subject to the constraints of real systems. We quantify the differences of our systems compared with traditional systems using latency and objective image fidelity measures. We use our novel systems to perform user studies into the effects of latency. Our high performance apparatuses allow experimentation at latencies lower than previously tested in comparable studies. The low latency apparatuses are designed to minimise what is currently the largest delay in traditional rendering pipelines and we find that the approach is successful in this respect. Our 3D low latency apparatus achieves lower latencies and higher fidelities than traditional systems. The conditions under which it can do this are highly constrained however. We do not foresee dataflow computing shouldering the bulk of the rendering workload in the future but rather facilitating the augmentation of the traditional pipeline with a very high speed local loop. This may be an image distortion stage or otherwise. Our latency experiments revealed that many predictions about the effects of low latency should be re-evaluated and experimenting in this range requires great care