The traditional tests are planned and designed at the early stages, but it is possible to execute test cases after implementing source code. Since there is a time difference between design stage and testing stage, by the time a software design error is found it will be too late. To solve this problem, this paper suggests a virtual pre-testing process. While the virtual pre-testing process can find software and testing errors before the developing stage, it can automatically generate and execute test cases with modeling and simulation (M&S) in a virtual environment. The first part of this method is to create test cases with state transition tree based on state diagram, which include state, transition, instruction pair, and all path coverage. The second part is to model and simulate a virtual target, which then pre-test the target with test cases. In other words, these generated test cases are automatically transformed into the event list. This simultaneously executes test cases to the simulated target within a virtual environment. As a result, it is possible to find the design and test error at the early stages of the development cycle and in turn can reduce development time and cost as much as possible.

This study examines the dialog-based language learning game (DB-LLG) realized in a 3D environment built with game contents. We designed the DB-LLG to communicate with users who can conduct interactive conversations with game characters in various immersive environments. From the pilot test, we found that several technologies were identified as essential in the construction of the DB-LLG such as dialog management, hint generation, and grammar error detection and feedback. We describe the technical details of our system POSTECH immersive English study (Pomy). We evaluated the performance of each technology using a simulator and field tests with users.

In this paper, we present a new three-dimensional (3D) virtual environment (3DVE) system named "QuViE/P", which can enhance quality of service (QoS), that users actually feel, as good as possible when resources of computers and networks are limited. To realize this, we focus on characteristics of user's perceptual quality evaluation on 3D objects. We propose an effective QoS control scheme for QuViE/P by introducing relationships between system's internal quality parameters and user's perceptual quality parameters. This scheme can appropriately maintain the QoS of the 3DVE system and it is expected to improve convenience when using 3DVE system where resources are insufficient. We designed and implemented a prototype of QuViE/P using a multiagent framework. The experiment results show that even when the computer resource is reduced to 20% of the required amount, the proposed scheme can maintain the quality of important objects to a certain level.

3D virtual environment provides a limited amount of information, mainly focusing on visual information. This is the main cause of users losing the sense of direction in the environment. Many researches for developing a navigation tools that address this problem have been carried out. In this study, a navigation tool is designed by applying topic map, one of the technologies for semantic web construction, to a 3D virtual environment. Topic map constructs a semantic link map by defining the connection relation between topics. According to an experiment done to evaluate the proposed navigation tool, the tool was more helpful in finding detailed object than highly represented objects. Also, it could be seen that providing the surrounding knowledge is effective for object selection by users when that target for searching is not defined.

In this paper, a novel projection-based method is presented to register partial 3D point clouds, acquired from a multi-view camera, for 3D reconstruction of an indoor scene. In general, conventional registration methods for partial 3D point clouds require a high computational complexity and much time for registration. Moreover, these methods are not robust for 3D point cloud which has a low precision. To overcome these drawbacks, a projection-based registration method is proposed. Firstly, depth images are refined based on both temporal and spatial properties. The former involves excluding 3D points with large variation, and the latter fills up holes referring to four neighboring 3D points, respectively. Secondly, 3D point clouds acquired from two views are projected onto the same image plane, and two-step integer mapping is applied to search for correspondences through the modified KLT. Then, fine registration is carried out by minimizing distance errors based on adaptive search range. Finally, we calculate a final color referring to the colors of corresponding points and reconstruct an indoor scene by applying the above procedure to consecutive scenes. The proposed method not only reduces computational complexity by searching for correspondences on a 2D image plane, but also enables effective registration even for 3D points which have a low precision. Furthermore, only a few color and depth images are needed to reconstruct an indoor scene. The generated model can be adopted for interaction with as well as navigation in a virtual environment.

Many immersive displays developed in previous researches are strongly influenced by the design concept of the CAVE, which is the origin of the immersive displays. In the view of human-scale interactive system for virtual environment (VE), the existing immersive systems are not enough to use the potential of a human sense further extent. The displays require more complicated structure for flexible extension, and are more restrictive to user's movement. Therefore we propose a novel multi-projector display for immersive VE with haptic interface for more flexible and dynamic interaction. The display part of our system named "D-vision" has a hybrid curved screen which consist of compound prototype with flat and curve screen. This renders images seamlessly in real time, and generates high-quality stereovision by PC cluster and two-pass technology. Furthermore a human-scale string-based haptic device will integrate with the D-vision for more interactive and immersive VE. In this paper, we show an overview of the D-vision and technologies used for the human-scale haptic interface.

In this paper, a new method for displaying a surface deformation is proposed to provide sufficient realism in virtual environment. The approach selected in this paper is based on the fuzzy model and it is sufficient that only one additional rule be added to the fuzzy model to display a surface deformation. Furthermore, designers can easily determine which parameters should be used and how much they should be changed in order to alter shapes as required. The proposed method, thus, is a simple, but effective technique that can also be applied to real time operation and makes it possible to act on several surface points simultaneously. The results of the computer simulation are also given to demonstrate the validity of the proposed algorithm.

Despite their attractive properties, networked virtual environments (net-VEs) are notoriously difficult to design, implement and test due to the concurrency, real-time and networking features in these systems. The current practice for net-VE design is basically trial and error, empirical, and totally lacks formal methods. This paper proposes to apply a Petri net formal modeling technique to a net-VE: NICE (Narrative Immersive Constructionist/Collaborative Environment), predict the net-VE performance based on simulation, and improve the net-VE performance. NICE is essentially a network of collaborative virtual reality systems called CAVE-(CAVE Automatic Virtual Environment). First, we present extended fuzzy-timing Petri net models of both CAVE and NICE. Then, by using these models and Design/CPN as the simulation tool, we have conducted various simulations to study real-time behavior, network effects and performance (latencies and jitters) of NICE. Our simulation results are consistent with experimental data.

The construction of photo-realistic 3D scenes from video data is an active and competitive area of research in the fields of computer vision, image processing and computer graphics. In this paper we address our recent work in this area. Unlike most methods of 3D scene construction, we consider the generation of virtual environments from video sequence with a video-cam's forward motion. Each frame is decomposed into sub-images, which are registered correspondingly using the Levenberg-Marquardt iterative algorithm to estimate motion parameters. The registered sub-images are correspondingly pasted together to form a pseudo-3D space. By controlling the position and direction, the virtual camera can walk through this virtual space to generate novel 2D views to acquire an immersive impression. Even if the virtual camera goes deep into this virtual environment, it can still obtain a novel view while maintaining relatively high resolution.

When we design a human interface of a computer-mediated communication (CMC) system, it is important to take a socio-behavioral approach for understanding the nature of the human communication. From this point of view, we conducted experimental observations and post-experimental questionnaires to investigate communicative characteristics in a teleconference using Fujitsu Habitat" visual telecommunication software. We experimentally held the following three kinds of small-group conferences consisting of five geographically distributed participants: (a) teleconference using a visual telecommunication system (Fujitsu Habitat"), (b) teleconference using a real-time keyboard telecommunication system of NIFTY-Serve and (c) live face to face physical conference. Analyses were made on (1) effects of the media on utterance behaviors of conference members, and (2) satisfaction of conference members with communicative functions of the media. Satisfaction was measured by a seven-level rating scale. We found that participants in a telconference held by using Habitat showed significant differences in contents of utterances and the rating of satisfaction with nine communicative functions compared with those of conferences held by using a real-time keyboard telecommunication system and a live face-to-face conference. These results suggest some features that could facilitate multi-participant on-line electronic conferences and conversations.