Showing papers in "International Journal of Virtual Reality in 2010"

A Survey of Augmented Reality Technologies, Applications and Limitations

Abstract: We are on the verge of ubiquitously adopting Augmented Reality (AR) technologies to enhance our percep- tion and help us see, hear, and feel our environments in new and enriched ways. AR will support us in fields such as education, maintenance, design and reconnaissance, to name but a few. This paper describes the field of AR, including a brief definition and development history, the enabling technologies and their characteristics. It surveys the state of the art by reviewing some recent applications of AR technology as well as some known limitations regarding human factors in the use of AR systems that developers will need to overcome.

Collaborative Virtual Surgery: Techniques, Applications and Challenges

Abstract: While considerable effort has been dedicated to improve medical education with virtual reality based surgical simulators, relatively little attention is given to the simulation of the collaborative procedures in distributed environments. In this paper, we first present a literature review of techniques involved in the development of collaborative simulators, including network architecture, transmission protocol, collaboration mechanism, schedule algorithm, collaborative user-interaction feature and haptic communication. We introduce the details of each technique and discuss the advantages and drawbacks. Then, we review some of the existing applications to illustrate how to apply these techniques to implement an efficient and robust collaborative simulator. Finally, we discuss the challenges that need to be addressed in the future.

PEGASE: A Generic and Adaptable Intelligent System for Virtual Reality Learning Environments

Abstract: The context of this research is the creation of human learning environments using virtual reality. We propose the integration of a generic and adaptable intelligent tutoring system (Pegase) into a virtual environment. The aim of this environment is to instruct the learner, and to assist the instructor. The proposed system is created using a multi-agent system. This system emits a set of knowledge (actions carried out by the learner, knowledge about the field, etc.) which Pegase uses to make informed decisions. Our study focuses on the representation of knowledge about the environment, and on the adaptable pedagogical agent providing instructive assistance.

Refinement of Surface Mesh for Accurate Multi-View Reconstruction

Abstract: In this paper we propose a pipeline for accurate 3D reconstruction from multiple images that deals with some of the possible sources of inaccuracy present in the input data. Namely, we address the problem of inaccurate camera calibration by including a method adjusting the camera parameters in a global structure-and-motion problem, which is solved with a depth map for representation that is suitable to large scenes. Secondly, we take the triangular mesh and calibration improved by the global method in the first phase to refine the surface both geometrically and radiometrically. Here we propose surface energy which combines photoconsistency with contour matching and minimize it with a gradient descent method. Our main contribution lies in effective computation of the gradient that naturally regularization and data terms by employing scale space approach. The results are demonstrated on standard high-resolution datasets and a complex outdoor scene.

Surface Reconstruction from Multi-View Stereo of Large-Scale Outdoor Scenes

Abstract: This article describes an original method to reconstruct a 3D scene from a sequence of images. Our approach uses both the dense 3D point cloud extracted by multi-view stereovision and the calibrated images. It combines depth-maps construction in the image planes with surface reconstruction through restricted Delaunay triangulation. The method may handle very large scale outdoor scenes. Its accuracy has been tested on numerous outdoor scenes including the dense multi-view benchmark proposed by Strecha et al. Our results show that the proposed method compares favorably with the current state of the art.

Emotion modeling and Interaction of NPCS in Virtual Simulation and Games

Abstract: Virtual simulations and games utilizing NPCs, or computer controlled agents, are more predominant now than ever. Many of these simulations suffer from a lack of effective, stimulating, and natural emotion-based behaviours in the interaction among the NPCs, as well as with the human players. This paper presents an easy-to-use, portable, diverging, and adaptive emotion model based on psychological and sociological research, for simulation and game designers to utilize easily in their virtual world. The proposed emotion model allows the player to better relate, understand and believe in characters in the virtual environment

Permutation Steganography for Polygonal Meshes Based on Coding Tree

Abstract: We propose a coding tree for permutation steganography in polygonal meshes. Instead of conceptually building a complete binary tree for remaining embedding/extracting primitives to encode/decode bitstream, our method lengthens bitstream by exploiting the coding tree of the primitives, a binary tree which is a little bit skewed. The coding tree has higher levels than the complete binary tree so that as experimental results show, the average capacity of our approach is more about 0.39 bit/vertex than that of Bogomjakov et al. [5], and the improvement of the maximal capacity comes up to 40% of Bogomjakov et al. [5]. Still, our method has the minimal capacity same with Bogomjakov et al. [5], and is simple and easy to implement as well. This ordering is obtained based on the mesh connectivity [14], making our method robust to geometric affine transformations. Also, the primitive rearrangement does not distort the cover media and cause suspicion of the hidden message

Image-based Modeling of Haussmannian Facades

Abstract: This paper describes techniques and algorithms for Haussmannian facade modeling. Although buildings are complex artificial objects which are difficult to interpret, Haussmannian buildings carry a more consistent typology and composition rhythm. By incorporating the architectural knowledge of the Haussmannian facade into an image analysis process, facade structure information can be automatically inferred. Moreover, in order to further refine the facade analysis, an image synthesis process is integrated and a feedback loop is created for producing more stable results. With this methodology, a solid technique and process for image-based modeling of Haussmannian or similar building facades have been established.

Natural Feature Detection on Mobile Phones with 3D FAST

Abstract: In this paper, we present a novel feature detection approach designed for mobile devices, showing optimized solutions for both detection and description. It is based on FAST (Features from Accelerated Segment Test) and named 3D FAST. Being robust, scale-invariant and easy to compute, it is a candidate for augmented reality (AR) applications running on low performance platforms. Using simple calculations and machine learning, FAST is a feature detection algorithm known to be efficient but not very robust in addition to its lack of scale information. Our approach relies on gradient images calculated for different scale levels on which a modified9 FAST algorithm operates to obtain the values of the corner response function. We combine the detection with an adapted version of SURF (Speed Up Robust Features) descriptors, providing a system with all means to implement feature matching and object detection. Experimental evaluation on a Symbian OS device using a standard image set and comparison with SURF using Hessian matrix-based detector is included in this paper, showing improvements in speed (compared to SURF) and robustness (compared to FAST)

Omnidirectional Free-viewpoint Rendering Using a Deformable 3-D Mesh Model

Abstract: This paper proposes a method to render free viewpoint images from omnidirectional videos using a deformable 3-D mesh model. In the proposed method, a 3-D mesh is placed in front of a virtual viewpoint and deformed by using the pre-estimated omnidirectional depth maps that are selected on the basis of position and posture of the virtual viewpoint. Although our approach is fundamentally based on the model-based rendering approach that renders a geometrically correct virtualized world, in order to avoid the hole problem, we newly employ a viewpoint-dependent deformable 3-D model instead of the use of a unified 3-D model that is generally used in the model based rendering approach. In experiments, free-viewpoint images are generated from the omnidirectional video captured by an omnidirectional multi camera system to show the feasibility of the proposed method for walk-through applications in the virtualized environment.

Exploring wireless mesh networks for collaborative augmented reality environments

Abstract: Augmented Reality (AR) has emerged as a technology able to greatly support the interaction between people and digital information by merging virtual objects with the real environment. So far, research in this field has been mainly focused on single-user scenarios with pre-stored digital data whose visualization needs to be appropriately and promptly aligned with physical objects. Instead, latest developments of AR also involve collaborative scenarios where several participants share the same AR environment, generating and exchanging data in real-time, and communicating with each other through VoIP. To this aim, in this work we consider networking issues and possible solutions, as they represent crucial aspects when dealing with collaborative AR environments. Through the use of a real testbed, we discuss how Wireless Mesh Networks (WMNs) can be practically employed to support communications in a department-wide AR environment without the need of a fixed infrastructure. We also analyze the performance limitations of this architecture and, finally, we evaluate a possible practical QoS solution to overcome them.

A Robust High-dimensional Data Reduction Method

Abstract: In this paper, we propose a robust high-dimensional data reduction method. The model assumes that the pixel reflec-tance results from linear combinations of pure component spectra contaminated by an additive noise. The abundance parameters appearing in this model satisfy positivity and additive constraints. These constraints are naturally expressed in a Bayesian literature by using appropriate abundance prior distributions. The posterior distributions of the unknown model parameters are then derived. The proposed algorithm consists of Bayesian inductive cognition part and hierarchical reduction algorithm model part. The pro-posed reduction algorithm based on Bayesian inductive cognitive model is used to decide which dimensions are advantageous and to output the recommended dimensions of the hyperspectral image. The algorithm can be interpreted as a robust reduction inference method for a Bayesian inductive cognitive model. Experimental results on high-dimensional data demonstrate useful properties of the proposed reduction algorithm.

Discretionary Access Controls for a Collaborative Virtual Environment

Abstract: As collaborative virtual environments (CVEs) are more widely used, participant access to CVE objects and information becomes a significant concern. In virtual reality games, storefronts, classrooms, and laboratories, for example, the need to control access to spaces and objects is integral to the security of activities taking place there. However, limited access controls are typically available in CVEs. Often, such controls are course-grained, only protecting against movements by unauthorized participants into specific areas. In answer to this deficiency, we offer a discretionary access control (DAC) system based on traditional concepts of users and groups, and tailored to the needs of a CVE. Our system, called WonderDAC, includes the ability to restrict movement into areas, as well as control interactions with objects. A basic WonderDAC prototype has been implemented within the Project Wonderland CVE.

3DUI-EF: Towards a Framework for Easy Empirical Evaluation of 3D User Interfaces and Interaction Techniques

Abstract: Designing usable and effective 3D User Interfaces and 3D Interaction Techniques is very challenging for Virtual Reality system developers and human factors specialists. Indeed, time consuming empirical evaluation is necessary to have an idea about the goodness of the 3D User Interface (3DUI) and the 3D Interaction Technique (3DIT) at the end of their development lifecycle. This may induce a huge loss of time if the result appears not to be satisfying in the end. Moreover, 3DUI evaluation is much more complex than 2D User Interfaces evaluation which is due to heterogeneous Virtual Reality (VR) devices and 3DIT. The aim of this work is to provide a framework allowing developers and experimenters to quickly evaluate 3DUIs and 3DITs during the design and the development lifecycle. The proposed framework is divided into two tools. The first one enables to create an evaluation protocol based on a knowledge database using two data mining algorithms, the "C4.5" to avoid from impossible combinations between devices and indicators and the "Spv Assoc Tree" to build a decision tree between indicators and factors. The second tool of the framework is an Evaluation Virtual Environment (EVE) to perform the evaluation according the protocol created with the first tool.

Avatar-based Intelligent Navigation for Online Shanghai Expo

Abstract: Shanghai Expo 2010 is an international event which will demonstrate the scientific, economic and cultural advance of the exhibiting countries. The local government launches a project named on-line Shanghai Expo in order to make the event accessible to people through Internet. Virtual reality technologies, especial intelligent virtual environment (IVE), are exploited to support the Expo. IVE, based on semantic, is the integration of Virtual Environment and Artificial Intelligence. It can improve the interaction between avatar and the virtual world by giving the objects in the environment semantic information. In this paper we employ intelligent virtual environment to build a virtual environment of realistic behavior and intelligent navigation.

Automatic 3D Reconstruction from a Single Catadioptric Omnidirectional Image

Abstract: In this paper we present a method for 3D urban reconstruction from a single catadioptric omnidirectional image. Firstly, we classify the catadioptric omnidirectional image to horizontal ground, vertical building surface and vertical background surface through the registration between catadioptric omnidirectional image and remote sensing image. According to the classification results, we recover the geometry based on the catadioptric projection model. The experiment shows that our method is feasible and realizes a precise 3D reconstruction for the city scenes.

A Model to Distinguish Between Educational and Training 3D Virtual Environments and its Application

Abstract: This paper proposes a model to identify education and/or training emphasis for 3D Virtual Environments. Through a survey of such applications specific characteristics of each emphasis were identified. Although few authors highlight the distinction between Virtual Environments for Education and Training, the correct definition of each of these types can facilitate the attainment of educational goals for the niche one wants to accomplish. In this study a special focus is given to the training applications, with the proposal of a standardization of the "training modes" based on a functional conceptual framework. At the end of the article a case study of a desktop Virtual Reality (VR) system for training will be presented. This system includes a maintenance sub-system in a Hydroelectric Energy Unit, using a "learn by doing" approach

Semantic Modeling Approach of 3D City Models and Applications in Visual Exploration

Abstract: In recent years, the necessity of the incorporation of semantic information into three-dimensional city models (3DCMs) has become a consensus in 3D GIS field. In order to provide practical support for visual applications concerned with semantics, this paper firstly presents an extended semantic model based on the CityGML standard, which was worked out for the general storage and representation of semantics. In this model, concepts like Room, Corridor and Stair are all derived from concept Space which corresponds to the concept of Room in CityGML. This extension will benefit the indoor structure representation. Geological feature is also supported by the model for the underground analysis. Next, for the promotion of semantic modeling by this model, a semi-automatic process of semantic enrichment is implemented in a data integration tool. It provides an adaptive way to link semantics with pure geometry. Finally, two typical cases of visual exploration are illustrated to prove the model’s practicability in a national 3D GIS project of China. One is indoor routing, which adopts this model to extract the geometric path and thus enrich traditional semantic-enhanced navigation routine; another case is unified profiler, where semantics are intergrated in order to fill up the cross section correctly and ensure the topological and semantic consistency.

Communications and Decisions of Autonomous Vehicles in Virtual Environments

Abstract: -In many virtual environments, autonomous objects, such as people and vehicles, are essential to increase the feeling of presence A goal is to have autonomous objects behave as humans, or in the case of vehicles, as if humans controlled them Such objects are known as intelligent autonomous objects We present a combination of a communication model and a decisionmaking model to achieve the goal of modeling autonomous objects that behave intelligently Both models are attached to autonomous objects that represent people and vehicles in a virtual environment This enables such an autonomous object to be an independent entity that is self-motivated and self-controlled These intelligent autonomous objects are able to communicate with other autonomous objects via their communication model according to decisions reached by their decision-making model The decision-making model relies on the communication model to investigate possible outcomes before making decisions The communication model defines senders, receivers, contents, and channels (media through which content is transferred) in realtime to gather desired information from specified objects The decision-making model is divided into two levels, the global level and the local level These work, respectively, with global information perceived by a perception model and the local information received by the communications model A group of logic rules are formulated as decision trees to model the process of making decisions on the basis of real-time activities We used traffic and people, in a virtual environments based driving simulator, as examples of intelligent communicating autonomous objects

Virtual Environment for an Ants-like Model

Abstract: In this paper we introduce an integrated virtual environment of ants-like agents based on ants' behavior. Our system can simulate the behavior of ants-like agents under various conditions and environment changes. In our model the ants are moving in random on an environment that contains a randomly distributed source of food. Ants move with some simple rules and can change direction according to environmental information. We test this model with various situations and conditions of the environment to study how the system works with the pheromone information. In the aim of realizing the practical implication of our model, a web-based computer simulation is given. This simulation enables the study and test for the model under different circumstances of the environmental conditions

Automating Terrain Texturing in Real-Time Using a Rule-Based Approach

Abstract: This publication proposes a novel approach to automatically colour and texture a given terrain mesh in real time. Through the use of weighting rules, a simple syntax allows for the generation of texture and colour values based on the elevation and angle of a given vertex. It is through this combination of elevation and angle that complex features such as ridges, hills and mountains can be described, with the mesh coloured and textured accordingly. The implementation of the approach is done entirely on the GPU using 2D lookup textures, delivering a great performance increase over typical approaches that pass colour and weighting information in the fragment shader. In fact, the rule set is abstracted enough to be used in conjunction with any colouring/texturing approach that uses weighting values to dictate which surfaces are depicted on the mesh

Recent Advances on Human Crowd Simulation

Abstract: Human crowd simulation is a new technology in the virtual reality field. Since it could simulate evacuation, it has strong demands in risk assessment for public buildings. In this paper we discuss the development of the main related research topics, including semantic description for virtual environments and crowd models which generate continuum human flow. Additionally, we introduce a system named Guarder that is designed for human crowd simulation and is suit for simulating evacuation in public buildings. We also demonstrate some simulation results of Guarder to show that it could efficiently simulate evacuation in a large-scale and complex environment.

Stereo Educational Game with Vision Based Interaction in Virtual Environment

Abstract: Interaction and immersion are crucial to educational game quality. Thus, a vision based marker location interaction and stereo rendering method for the game are proposed. This approach could support the players to have more intuitive interaction and more immersion feeling. First, a general architecture of the educational game based on computer vision marker localization interaction was presented. Then, a new method to vision based marker localization and identification interaction was studied. The basic idea of this interaction is using a static camera to track the position and pose information of the marker in the handheld device. So the game system can judge the operation purposes of players such as pick up or put down a virtual objects based on the position and pose information of the marker easily. The experiment result shows this interactive method has a high tracking accuracy. Furthermore, rendering module of the game is designed by using a stereo rendering method, so it can produce stereo vision for players. Last, a feeding animal game for children is realized to verify the presented approaches. Children can carry different food to different animals by a handheld device with marker so that they can learn what food the animals like. The running result illustrates that the presented approaches are effective, and they can provide a natural interaction for game in virtual environment

Assessment of Stereoscopic Multi-resolution Images for a Virtual Reality System

Abstract: A camera and monitor system that projects actual real-world images has yet to be developed due to the technical limitation that the existing cameras cannot simultaneously acquire high-resolution and wide-angle images. In this research, we try to resolve this issue by superimposing images; a method which is effective because the entire wide-angle image does not necessarily need to be of high resolution because of perceptual characteristics of the human visual system. First, we examined the minimum resolution required for the field of view, which indicated that a triple-resolution image where positions more than 20 and 40 deg from the center of the visual field were decreased to 25% and approximately 11% of the resolution of the gaze point, respectively, was perceived as similar to a completely high-resolution image. Next, we investigated whether the participants could distinguish between the original completely high-resolution image and processed images, which included triple-resolution, dual-resolution, and low-resolution images. Our results suggested that the participants could not differentiate between the triple-resolution image and the original image. Finally, we developed a stereoscopic camera system based on our results

Fast 3D Shape Recovery from Shadows Projected on Arbitrary Curved Surfaces

Abstract: The shadow based 3D surface reconstruction methods usually assume that shadows are projected on planar surfaces. However, shadows are often projected on curved surfaces in the real scene. Recently, the shadow graph has been proposed for representing shadow information efficiently, and for recovering 3D shapes from shadows projected on curved surfaces. Unfortunately, the method requires a large computational cost and is weak to the image intensity noises. In this paper, we introduce 1D shadow graphs which can represent shadow information quite efficiently, and can be used for recovering 3D shapes with much smaller computational costs than before. We also extend our method, so that we can recover 3D shape quite accurately by using shading information as well as shadow information. The proposed method is tested by using the real and synthetic images.

Understanding the affordances of navigation metaphors in a collaborative virtual environment

Abstract: When designing a collaborative virtual environment (CVE) one important decision is to identify the right interaction technique to be used. This paper takes the position that the interaction techniques used in a CVE have an effect on user’s collaborative experience. Paper investigates the effect of three 3D navigation techniques on user’s experience when interacting in a CVE. We report the affordances of navigation techniques using different aspects of user’s experience such as awareness, perception of collaborative effort, presence and satisfaction. 40 subjects were grouped in pairs of two users to perform a collaborative navigation task. Our results show that giving the user’s a direct control of their actions influences positively their copresence and awareness. A direct visual feedback of the partner’s point of view is beneficial for the copresence and the awareness. Finally, the space reference and the orientation in the virtual environment (VE) have an impact on the user involvement. These results provide an initial set of guidelines for the design of collaborative virtual environments.

Mobile AR Requirements for Location Based Social Networks

Abstract: Utilizing the novel User Interface (UI) technology of Augmented Reality (AR) in mobile phones provides significant advantages for Location Based Social Networks (LBSN) via powerful UI that allows the user to see the world through AR view rather than via a traditional map view. Compared to use of a map based interface, it is much easier for the user to understand where the nearby friends and points of interests are located when using a mobile AR interface to access the information of LBSN services. Recent development in the commercially available high end mobile phones has made it a viable device to use globally available AR services, but there still exist some limitations when it comes to LBSN services. Especially demanding is the need to include constantly moving friends reliably and accurately as annotated objects into the AR view of a user. In this article we show for the first time that mobile phones can be utilized to create mobile AR based LBSN services and create an experimental system to validate this. We present the most important use cases of the mobile AR based LBSN services, define the key requirements for the system, and analyze how the current high end mobile phones meet these. We point out the main challenges in position and orientation accuracy, data transfer and power consumption, as well as solutions to improve these. We present results from end-user studies and our experimental system we have created to study mobile AR interface for the LBSN services, and conclude that the mobile phones can be used for creation of these services when the key challenges are resolved

Human-Guided Simulation for Lunar Rover in Virtual Environment

Abstract: Lunar rover development involves a large amount of validation works in realistic operational conditions, including its mechanical subsystem and on-board software. The traditional simulation step is to construct model, input parameters, execute a simulation, and visualize the results. However, a more insight and higher productivity can be achieved if these activities are guided by human simultaneously. In this paper, a human-guided simulation method for China lunar rover simulation environment (CLRSE) that affords real time capabilities with high fidelity has been presented. It studied the input of kinematics simulation, analyzed a quick steering method of complex dynamic interactions between wheel and soft moon ground, and presented a way of path choosing by human guided. And the application which runs on PC Cluster and Silicon Graphics is also developed in this environment.

3D Anthropomorphic Avatar Model Based on Multi-layered Representation

Abstract: Avatars are virtual characters making the communication between user and machine more natural and interactive. The main advantage of using avatars within interfaces is to allow user to interact intuitively with the system by giving him the illusion of communicating with a real human. This illusion is obtained by mimicking human communication, i.e. giving avatar the ability of expressing emotions through facial and body language. We proposed the method based on multi-layered representation for a kind of 3D anthropomorphic avatar, and validated it as an information presenter. The way of controlling the avatar's emotion is to use parameterized facial muscle model and skeleton skinning, scheduled with multi-thread. Then a series of naturalistic avatar animation produced.

Agile Development of WebVR Applications

Abstract: This paper presents a novel "Roll and Raid" WebVR development model to solve the problems of conventional WebVR development practices. Firstly, agile methodology is introduced into the life cycle of developing WebVR. Secondly, some principles are further proposed to guide the entire WebVR development process. We choose some typical WebVR projects to verify its effectiveness. The experimental results show that our proposed "Roll and Raid" model is much advantageous over conventional WebVR development methods with lower cost, higher efficiency, stronger adaptiveness and easier team management.