Tolga K. Çapin

Anyone for Tennis

In this paper we present a virtual tennis game. We describe the creation and modeling of the virtual humans and body deformations, also showing the real-time animation and rendering aspects of the avatars. We focus on the animation of the virtual tennis ball and the behavior of a synthetic, autonomous referee who judges the tennis games. The networked, collaborative, virtual environment system is described with special reference to its interfaces to driver programs. We also mention the virtual reality (VR) devices that are used to merge the interactive players into the virtual tennis environment, together with the equipment and technologies employed for this exciting experience. We conclude with remarks on personal experiences during the game and on future research topics to improve parts of the presented system.

Nonverbal communication interface for collaborative virtual environments

Nonverbal communication is an important aspect of real-life face-to-face interaction and one of the most efficient ways to convey emotions, therefore users should be provided the means to replicate it in the virtual world. Because articulated embodiments are well suited to provide body communication in virtual environments, this paper first reviews some of the advantages and disadvantages of complex embodiments. After a brief introduction to nonverbal communication theories, we present our solution, taking into account the practical limitations of input devices and social science aspects. We introduce our sample of actions and implementation using our VLNET (Virtual Life Network) networked virtual environment and discuss the results of an informal evaluation experiment.

Virtual human representation and communication in VLNet

Using virtual humans to represent participants promotes realism in networked VEs. Different message types used to animate the human body and face impose varying network requirements, as analyzed here.

The HUMANOID Environment for Interactive Animation of Multiple Deformable Human Characters

We describe the HUMANOID environment dedicated to human modeling and animation for general multimedia, VR, and CAD applications integrating virtual humans. We present the design of the system and the integration of the various features: generic modeling of a large class of entities with the BODY data structure, realistic skin deformation for body and hands, facial animation, collision detection, integrated motion control and parallelization of computation intensive tasks.

MPEG-4: Audio/video and synthetic graphics/audio for mixed media

Abstract MPEG-4 addresses coding of digital hybrids of natural and synthetic, aural and visual (A/V) information. The objective of this synthetic/natural hybrid coding (SNHC) is to facilitate content-based manipulation, interoperability, and wider user access in the delivery of animated mixed media. SNHC will support non-real-time and passive media delivery, as well as more interactive, real-time applications. Integrated spatial-temporal coding is sought for audio, video, and 2D/3D computer graphics as standardized A/V objects. Targets of standardization include mesh-segmented video coding, compression of geometry, synchronization between A/V objects, multiplexing of streamed A/V objects, and spatial-temporal integration of mixed media types. Composition, interactivity, and scripting of A/V objects can thus be supported in client terminals, as well as in content production for servers, also more effectively enabling terminals as servers. Such A/V objects can exhibit high efficiency in transmission and storage, plus content-based interactivity, spatial-temporal scalability, and combinations of transient dynamic data and persistent downloaded data. This approach can lower bandwidth of mixed media, offer tradeoffs in quality versus update for specific terminals, and foster varied distribution methods for content that exploit spatial and temporal coherence over buses and networks. MPEG-4 responds to trends at home and work to move beyond the paradigm of audio/video as a passive experience to more flexible A/V objects which combine audio/video with synthetic 2D/3D graphics and audio.

Crowd modelling in collaborative virtual environments

1. ABSTRACT This paper presents a crowd modelling method in Collaborative Virtual Environment (CVE) which aims to create a sense of group presence to provide a more realistic virtual world. An adaptive display is also presented as a key element to optimise the needed information to keep an acceptable frame rate during crowd visualisation. This system has been integrated in the several CVE platforms which will be presented at the end of this paper.

A Flexible Architecture for Virtual Humans in Networked Collaborative Virtual Environments

Complex virtual human representation provides more natural interaction and communication among participants in networked virtual environments, hence it is expected to increase the sense of being together within the same virtual world. We present a flexible framework for the integration of virtual humans in networked collaborative virtual environments. A modular architecture allows flexible representation and control of the virtual humans, whether they are controlled by a physical user using all sorts of tracking and other devices, or by an intelligent control program turning them into autonomous actors. The modularity of the system allows for fairly easy extensions and integration with new techniques making it interesting also as a testbed for various domains from “classic” VR to psychological experiments. We present results in terms of functionalities, example applications and measurements of performance and network traffic with an increasing number of participants in the simulation.

Three-Dimensional Media for Mobile Devices

This paper aims at providing an overview of the core technologies enabling the delivery of 3-D Media to next-generation mobile devices. To succeed in the design of the corresponding system, a profound knowledge about the human visual system and the visual cues that form the perception of depth, combined with understanding of the user requirements for designing user experience for mobile 3-D media, are required. These aspects are addressed first and related with the critical parts of the generic system within a novel user-centered research framework. Next-generation mobile devices are characterized through their portable 3-D displays, as those are considered critical for enabling a genuine 3-D experience on mobiles. Quality of 3-D content is emphasized as the most important factor for the adoption of the new technology. Quality is characterized through the most typical, 3-D-specific visual artifacts on portable 3-D displays and through subjective tests addressing the acceptance and satisfaction of different 3-D video representation, coding, and transmission methods. An emphasis is put on 3-D video broadcast over digital video broadcasting-handheld (DVB-H) in order to illustrate the importance of the joint source-channel optimization of 3-D video for its efficient compression and robust transmission over error-prone channels. The comparative results obtained identify the best coding and transmission approaches and enlighten the interaction between video quality and depth perception along with the influence of the context of media use. Finally, the paper speculates on the role and place of 3-D multimedia mobile devices in the future internet continuum involving the users in cocreation and refining of rich 3-D media content.

A dead-reckoning algorithm for virtual human figures

In networked virtual environments, when the participants are represented by virtual human figures, the articulated structure of the human body introduces a new complexity in the usage of the network resources. This might create a significant overhead in communication, especially as the number of participants in the simulation increases. In addition, the animation should be realistic, as it is easy to recognize anomalies in the virtual human animation. This requires real-time algorithms to decrease the network overhead while considering characteristics of body motion. The dead-reckoning technique is a way to decrease the number of messages communicated among the participants, and has been used for simple non-articulated objects in popular systems. The authors introduce a dead-reckoning technique for articulated virtual human figures based on Kalman filtering, discuss main issues and present experimental results.

Efficient modeling of virtual humans in MPEG-4

This and the accompanying paper present an overview of the face and body animation object in the MPEG-4 Version 2 standard. The MPEG-4 standard includes the representation, compression of virtual human models and their interface with other MPEG-4 objects, with bit rate requirements as low as 1 Kbit/second. In this paper we give an overview of geometrical modeling techniques for the FBA object, and in the accompanying paper we describe the animation techniques.