Evaluation of 2D and 3D glove input applied to medical image analysis

We describe a series of experiments that compared 2D/3D input methods for selection and positioning tasks related to medical image analysis. For our study, we chose a switchable P5 Glove Controller, which can be used to provide both 2DOF and 6DOF input control. Our results suggest that for both tasks the overall performance and accuracy can be improved when the input device with more degrees of freedom (DOF) is used for manipulation of the visualized medical data. 3D input turned out to be more beneficial for the positioning task than for the selection task. In order to determine a potential source of the difference in the task completion time between 2D and 3D input, we also investigated whether there was a significant difference between 2DOF and 6DOF input methods with regard to the time spent on task-specific basic manipulations.     

Interaction techniques in desktop virtual environment: the study of visual feedback and precise manipulation method

Gesture-based systems allow users to interact with a virtual reality application in a natural way. Visual feedback for the gesture-based interaction technique has an impact on the performance and the hand instability making the manipulation of the object less precise. This paper investigated two new interaction techniques in a virtual environment. It describes the influence of natural and non-natural virtual feedback in the selection process using the GITDVR-G interaction technique, which consists of a grasping visual feedback. The GITDVR-G was evaluated in a virtual knee surgery training system. The results showed that it was effective in terms of the task completion time, and that the participants preferred the natural grasping visual feedback. Besides that, the precise manipulation in a newly-designed interaction technique (Precise GITDVR-G) was evaluated. The Precise GITDVR-G includes a normal manipulation mode and a precise manipulation mode that can be triggered by hand gestures. During the precise manipulation mode, an inset view will appear and move with the selected object to provide a better view to users, while the movements of the virtual hand are scaled down to improve the precision. Four different configurations of the precise manipulation technique were evaluated, and the results showed that the unimanual control method with an inset view performed better in terms of the task performance time and the subjective feedback. The finding suggested that the realistic virtual grasping visual feedback can be applied in a virtual hand interaction technique, and that the inset view feature is helpful in the precise manipulation.     

Working with tweets vs. working with chats: An experiment on collaborative problem solving

This papers aims to explore how “working with tweets” differs from “working with chats”. With eight experimental sessions involving 120 Italian students, we investigate how the well known 140-characters limit and other subtle differences between Twitter and a typical instant messenger affect group problem solving performances. In our laboratory experiment, teams of the same size carry out a problem solving task communicating via Twitter or Skype instant messaging. Comparative group performance is measured in terms of successful task completion time. Our results show that the lower number and volume of text messages exchanged via Twitter does not negatively affect group performance: Twitter teams are just as effective as Skype instant messaging teams. These results can be interpreted in accordance with the latest developments in multiple media choice and virtual team effectiveness theories, disclosing interesting windows of opportunities for “working with tweets” in the forthcoming organizational settings.     

面向沉浸式流场可视化的多视图数据管理方法

由于沉浸式环境下的三维交互方式对二维界面操作不够友好,使得依赖于二维列表界面的流场数据管理任务变得复杂且低效。为了实现沉浸式虚拟环境下对流场数据高效的组织和管理,增强用户对流场空间信息的理解,提出一种基于多视图结合交互的沉浸式流场可视化数据块管理方法。该方法构建了一个三维小视图用于提供场景概览,并通过“主视图交互+小视图辅助“”小视图交互+主视图反馈”等多种多视图组合交互方式完成对多块流场数据的管理交互操作。最后构建了一个基于手势的沉浸式流场可视化系统,定义多项交互任务,从学习时长、完成时间和用户反馈几个方面对比了多视图方法和传统交互方法差异。实验结果表明,相比于传统交互方法,多视图方法可以显著提高数据管理任务的效率。     

Two‐Finger Gestures for 6DOF Manipulation of 3D Objects

Multitouch input devices afford effective solutions for 6DOF (six Degrees of Freedom) manipulation of 3D objects. Mainly focusing on large‐size multitouch screens, existing solutions typically require at least three fingers and bimanual interaction for full 6DOF manipulation. However, single‐hand, two‐finger operations are preferred especially for portable multitouch devices (e.g., popular smartphones) to cause less hand occlusion and relieve the other hand for necessary tasks like holding the devices. Our key idea for full 6DOF control using only two contact fingers is to introduce two manipulation modes and two corresponding gestures by examining the moving characteristics of the two fingers, instead of the number of fingers or the directness of individual fingers as done in previous works. We solve the resulting binary classification problem using a learning‐based approach. Our pilot experiment shows that with only two contact fingers and typically unimanual interaction, our technique is comparable to or even better than the state‐of‐the‐art techniques.     

Two methods for the computation of nonlinear modes of vibrating systems at large amplitudes

The aim of this paper is to present two methods for the calculation of the nonlinear normal modes of vibration for undamped nonlinear mechanical systems: the time integration periodic orbit method and the modal representation method. In the periodic orbit method, the nonlinear normal mode is obtained by making the continuation of branches of periodic orbits of the equation of motion. The terms “periodic orbits” means a closed trajectory in the phase space, which is obtained by time integration. In the modal representation method, the nonlinear normal mode is constructed in terms of amplitude, phase, mode shape, and frequency, with the distinctive feature that the last two quantities are amplitude and total phase dependent. The methods are compared on two DOF strongly nonlinear systems.     

Seamless interaction in virtual reality

Jot is a novel research interface for virtual reality modeling. This system seamlessly integrates and applies a variety of virtual and physical tools, each customized for specific tasks. The Jot interface not only moves smoothly from one tool to another but also physically and cognitively matches individual tools to the tasks they perform. In particular, we exploit the notion that gestural interaction is more direct, in many cases, than traditional widget based interaction. We also respect the time tested observation that some operations-even conceptually three dimensional ones-are better performed with 1D or 2D input devices, whereas other operations are more naturally performed using stereoscopic views, higher DOF input devices, or both. Ultimately we strive for a 3D modeling system with an interface as transparent as the interaction afforded by a pencil and a sheet of paper. For example, the system should facilitate the tasks of drawing and erasing and provide an easy transition between the two. Jot emerged from our previous work on a mouse based system, called Sketch, for gesturally creating imprecise 3D models. Jot extends Sketch's functionality to a wider spectrum of modeling, from concept design to detailed feature based parametric parts. Jot also extends the interaction in Sketch to better support individual modeling tasks. We extended Sketch's gestural framework to integrate interface components ranging from traditional desktop interface widgets to context sensitive gestures to direct manipulation techniques originally designed for immersive VR     

Manipulating subjective realism and its impact on presence: Preliminary results on feasibility and neuroanatomical correlates

The feeling of presence has been shown to be an important concept in several clinical applications of virtual reality. Among the factors influencing presence, realism factors have been examined extensively from the angle of objective realism. Objective realism has been manipulated by altering numerous technological characteristics such as pictorial quality, texture and shading, or by adding more sensory information (i.e., smell, touch). Much less studied is the subjective (or perceived) realism, the focus of the two pilot studies reported in this article. In Study 1, subjective realism was manipulated in order to assess the impact on the feeling of presence. Method: Presence was measured in 31 adults after two immersions in virtual reality. Participants were immersed in a neutral/irrelevant virtual environment and subsequently subjected to the experimental manipulation. Participants in the experimental condition were falsely led to believe that they were immersed live in real time in a “real” room with a “real” mouse in a cage. In the control condition, participants believed they were immersed in a replica of the nearby room. All participants were actually immersed in the exact same virtual environment. Results: A manipulation check revealed that 80% of the participants believed in the deception. A 2 Times by 2 Conditions repeated measure ANOVA revealed that leading people to believe they were seeing a real environment digitized live in virtual reality increased their feeling of presence compared to the control condition. In Study 2, the same experimental design was used but with simultaneous functional magnetic resonance imaging (fMRI) in order to assess brain areas potentially related to the feeling of presence. fMRI data from five participants were subjected to a within subject fixed effect analysis to verify differences between the experimental immersion (higher presence) and the control immersion (lower presence). Results revealed a statistically significant difference in left and right parahippocampus areas. Conclusion: Results are discussed according to layers of presence and consciousness and the meaning given to experiences occurring in virtual reality. Some suggestions are formulated to target core presence and extended presence.     

Computer-aided surgery planning and rehearsal at Mayo Clinic

The Biomedical Imaging Resource at the Mayo Clinic has been involved in the design and implementation of computer-based techniques for comprehensive and fully-interactive display and analysis of biomedical images since the 1970s. The algorithms and programs Mayo Clinic has developed have been integrated into a software system called Analyze. This system has been used in the planning and rehearsal of numerous operations, including some special surgeries, such as the separation of joined twins. More than 10 years' experience using computers to plan operations has led Mayo Clinic to design the Virtual Reality Assisted Surgery Program (VRASP) for eventual use during craniofacial, orthopedic, prostate and neurological surgery. VRASP lets surgeons view 3D renderings of CT and MRI data and permits interactive virtual display manipulation. In essence, as doctors use interactive technology and computer-generated 3D images of patients' bodies to plan and rehearse surgery, so the program brings pre-surgery planning and rehearsal into line with what happens on the operating table, to make the surgical procedure more effective, less risky and less expensive     

Effects of Travel Modes on Performances and User Comfort: A Comparison between ArmSwinger and Teleporting

The commercialization of Head-Mounted Displays (HMDs) aimed at the general public has led several videogame and virtual reality companies to offer new modes for continuous travel, in addition to commonly implemented instantaneous travel modes such as the Teleporting metaphor. These new modes include the ArmSwinger metaphor, seen as “more natural.” Yet unlike Teleporting mode, ArmSwinger mode has so far not been studied. Our study was designed to fill this gap, by comparing the effects of these two travel modes implemented on an HTC Vive in terms of performance and user comfort. We collected two measures of performance (effectiveness and efficiency) and three measures of user comfort (cybersickness, user experience, and cognitive load). Results showed that (1) no significant difference was found in completion time between ArmSwinger mode and Teleporting mode, even if ArmSwinger mode seems more effective; (2) ArmSwinger mode caused more cybersickness than Teleporting mode in terms of nausea; (3) ArmSwinger mode produced a more negative user experience than the Teleporting mode in relation to appealingness qualities; and (4) ArmSwinger mode created a higher cognitive load than Teleporting mode in relation to the physical demand, effort, and frustration dimensions.     

CUDA-based real-time hand gesture interaction and visualization for CT volume dataset using leap motion

Touchless interaction has received considerable attention in recent years with benefit of removing barriers of physical contact. Several approaches are available to achieve mid-air interactions. However, most of these techniques cause discomfort when the interaction method is not direct manipulation. In this paper, gestures based on unimanual and bimanual interactions with different tools for exploring CT volume dataset are designed to perform the similar tasks in realistic applications. Focus + context approach based on GPU volume ray casting by trapezoid-shaped transfer function is used for visualization and the level-of-detail technique is adopted for accelerating interactive rendering. Comparing the effectiveness and intuitiveness of interaction approach with others by experiments, ours has a better performance and superiority with less completion time. Moreover, the bimanual interaction with more advantages is timesaving when performing continuous exploration task.     

European virtual classrooms: building effective “virtual” educational experiences

This paper presents Learning@Europe, an educational service, supported by VR, that has involved in year 2004–2005 more than 1,000 students from 6 different European countries. L@E has fostered the creation/reinforcement of three different kinds of communities: (1) the classroom community (reinforcing the bonds among students, and between students and their teachers), (2) communities among different schools competing together through 3D environments, (3) a global community (roughly involving 20% of the total) of all the teachers and students. A similar situation was created, at regional level, in the Italian Region of Lombardy, involving nearly 800 individuals. Given that the behaviours of the different communities in the two projects were very similar, it seems to be arguable that a pattern of community building through virtual environments has been detected. The important facts (detected by surveys of teachers and students, inspection, direct observation, qualitative data analysis) about these communities are: (1) the depth of the pedagogical impact, in terms of increased knowledge (about history and related subjects), skills (use of functional English, use of ICT in learning/teaching processes, group work) and attitudes (more curiosity towards history, increased motivation in school activities, improved respect and interest for other cultures). (2) The engagement of all the participants, with very high level of customer satisfaction. (3) The depth of the social impact, reinforcing existing relationships (within the same class) and creating new ones. The key feature of this success apparently lies in the sense of “social virtual presence”, that is, a feeling of being engaged in a virtual situation, so strong that the technological means become “transparent” and the social situation (meant at different levels and for different time frames) becomes “the king”. The paper will present the project, its main features and its outcomes, eventually discussing the role of social virtual presence into building effective and lively communities.     

Generation of natural motions for redundant multi‐joint systems: A differential‐geometric approach based upon the principle of least actions

This article challenges Bernstein's problem of redundant degrees of freedom (DOF) that remains unsolved from both the standpoints of physiology and robotics. A rather simpler but difficult control problem of movements of human‐like multi‐joint reaching with excess DOF is analyzed from Newtonian mechanics and differential geometry. It is shown that, regardless of ill‐posedness of inverse kinematics for such a redundant system, a simpler control signal composed of a well‐tuned (synergistic) combination of task‐space position feedback (corresponding to spring‐like forces) and joint velocity feedback (viscous‐like forces) leads to a skilled motion of reaching in a natural way without solving inverse kinematics or dynamics. Fundamental characteristics of human skilled multi‐joint movements such as (1) generation of a quasi‐straight line trajectory of the endpoint and (2) a little “variability” in task space but notable “variability” in joint space are analyzed from the concepts of “stability on an EP (equilibrium‐point) manifold” and “transferability to an EP submanifold.” It is claimed that the control signal exerts torques on joints of the whole arm just like a single virtual‐spring drawing the endpoint of the arm to the target while giving a specified viscosity to each joint. This leads to an interpretation that skilled reaching movements emerge through formation of a set of neuro‐motor signals exerting relevant group of muscles to generate a total potential energy equivalent to that of the spring. Discussions are presented on how such control signals in case of human reaching can be generated in a feedforward manner with capability of anticipatory adjustments of stiffness. © 2005 Wiley Periodicals, Inc.     

Comparison of database interfaces for application programming

The historical evolution of interfaces to databases at the application programming level is analyzed. Emphasis is put on aspects of the data manipulation operations rather than on the data model that they address.Four phases are distinguished in this evolution: “call” interfaces, simple language extensions, non-procedural languages embedded in general purpose languages, and integrated languages.The evolution is explained in terms of the growing needs for more reliable programs written in high level languages, for which programmer efficiency is more important than machine efficiency.     

Accurate arithmetic for vector processors

In addition to the four elementary arithmetic operations, more advanced electronic computers such as vector and parallel computers often provide a number of compound operations as additional elementary operations. If pipelined compound operations like “multiply and add,” “accumulate,” and “multiply and accumulate” contribute essentially to the high speed of the system. Accuracy requirements lead to very similar operations. We identify a set of operations which meet both requirements: high speed and accuracy. After a brief discussion of implementation techniques for the simpler of these operations we present two methods and circuits which allow a fast and correct computation of the more complicated of these operations: “accumulate” and “multiply and accumulate.” The first method computes sums and dot products by making use of a matrix-shaped and pipelined arrangement of adders which cover the full floating-point range. The second method requires some local memory on the arithmetic unit. It permits a drastic reduction in the number of adders required. Both methods can also be used to build a fast arithmetic unit for microcomputers in VLSI technology.     

Exploring high-order three dimensional virtual elements: Bases and stabilizations

We present numerical tests of the virtual element method (VEM) tailored for the discretization of a three dimensional Poisson problem with high-order “polynomial” degree (up to $p=10$). Besides, we discuss possible reasons for which the method could return suboptimal/wrong error convergence curves. Among these motivations, we highlight ill-conditioning of the stiffness matrix and not particularly “clever” choices of the stabilizations. We propose variants of the definition of face/bulk degrees of freedom, as well as of stabilizations, which lead to methods that are much more robust in terms of numerical performances.     

虚拟现实建模技术在数字化发射场中的应用

建立数字化发射场是卫星发射信息化和应急保障的基础。本文结合某卫星发射场实时性和交互性视景仿真实现的特点,采用基于三维几何模型的建模及动态显示技术的虚拟场景创建方法,讨论了虚拟漫游系统中建模流程、方法,以及关键技术的实现,分析了通用的三维场景建模的技术路线和流程,给出了地物、天空和实体模型构建的实际解决方案、方法,讨论了基于MultiGen Creator的模型格式转换、纹理贴图、模型简化、LOD技术、DOF技术等建模关键技术。采用MultiGen Creator和Vega软件平台,开发出了一个桌面型的虚拟发射场仿真系统,实现了发射场的数字化和卫星发射的实时仿真。     

Mobile manipulation: The robotic assistant

Mobile manipulation capabilities are key to many new applications of robotics in space, underwater, construction, and service environments. This paper discusses the development of robotic “assistance” capabilities to aid workers in the accomplishment of a variety of physical operations and presents various control strategies developed for vehicle-arm coordination, compliant motion tasks, and cooperative manipulation between multiple platforms. These strategies have been implemented on two holonomic mobile platforms designed and built at Stanford in collaboration with Oak Ridge National Laboratories and Nomadic Technologies.     

A gesture-free geometric approach for mid-air expression of design intent in 3D virtual pottery

The advent of depth cameras has enabled mid-air interactions for shape modeling with bare hands. Typically, these interactions employ a finite set of pre-defined hand gestures to allow users to specify modeling operations in virtual space. However, human interactions in real world shaping processes (such as pottery or sculpting) are complex, iterative, and continuous. In this paper, we show that the expression of user intent in shaping processes can be derived from the geometry of contact between the hand and the manipulated object. Specifically, we describe the design and evaluation of a geometric interaction technique for bare-hand mid-air virtual pottery. We model the shaping of a pot as a gradual and progressive convergence of the pot’s profile to the shape of the user’s hand represented as a point-cloud (PCL). Thus, a user does not need to learn, know, or remember any gestures to interact with our system. Our choice of pottery simplifies the geometric representation, allowing us to systematically study how users use their hands and fingers to express the intent of deformation during a shaping process. Our evaluations demonstrate that it is possible to enable users to express their intent for shape deformation without the need for a fixed set of gestures for clutching and deforming a shape.     

The influence of disposition and social ties on trust in new virtual teammates

With the increased presence of social media tools such as LinkedIn and Facebook, social network information is now commonplace. Social media websites prominently display the social distance or so-called “degrees of separation” among users, effectively allowing people to view their shared social ties with others, including prospective teammates they have not met. Through the presentation and manipulation of social network information, this longitudinal experiment investigated whether dispositional and relational variables contribute to “swift trust” among new virtual teammates. Data from 74 participants were collected to test a path analytic model predicting that social ties and propensity to trust influence perceptions of a new teammate’s trustworthiness (ability, benevolence, and integrity) as well as the willingness to trust that new teammate when given the opportunity to do so. Path analysis indicated good model fit, but showed no significant evidence that social ties or propensity to trust affect perceived trustworthiness at the initial point of team engagement. Additionally, only one component of perceived trustworthiness (perceived ability) and propensity to trust were found to predict trusting behavior towards a new, unknown, teammate.