Tatsuhiro Yonekura

Time-stamp service makes real-time gaming cheat-free

Assuming time-stamp servers that we can trust exist everywhere in the Internet, we propose a cheat-proof protocol for real-time gaming that has the minimum latency. The assumptions are: 1) Time-stamp servers are available near each player that issue serially numbered time stamps. 2) There is no communication break down between the player and the nearest time-stamp server. By this protocol, each player sends its own action to the other player and also sends its hash to the nearest time-stamp server. The time-stamp server sends back to the player the signed hash with time and a serial number involved. The signature is an undeniable evidence of the action. The actions are checked if they are compatible with the hashes and the signed hashes are checked if they have the correct time and if the serial numbers are contiguous. This verification can be done as a batch after the game is finished. The latency in this protocol is only the packet traveling time from a player to another.

A Proposal of Dead Reckoning Protocol in Distributed Virtual Environment based on the Taylor Expansion

In this paper, we studied the relationship between the accuracy of the dead reckoning data and the update interval in a distributed virtual environment (DVE). We have already shown that numerical analysis can be applied to the dead reckoning data between frames using parametrics calculated from the data over the last several frames based on polynomial models. Based on the above polynomial models, we proposed the new dead reckoning method to extrapolate the attribute data which arrives at discrete time period. We showed that theoretical models which approximate the statistical error of dead reckoning data can be formulated based on parameters such as the update interval and changes in the data. Theoretical models showed that the average error of proposed method is less than that of current method. Finally, we evaluate the validity of the proposed method with the comparison of current method by conducting experiments with the pen motion of a series of letters written by human. We confirmed that the proposed method can decrease the extrapolation error in comparison with current method in average

Dynamic Data Allocation Scheme for Multi-server Web-Based MORPG System

Recently, due to the spread of broadband access to the Internet, the speeding up JavaScript on Web browsers and the development of communication technology such as Ajax, a variety of Web applications are provided. However, the access congestion to the Web server and the lower usability in case of higher frequent communication are major problems on the Web application. We have investigated the bottleneck in Web-based MORPG system and proposed the load-distribution technique using multiple Web servers[8]. This technique uses a dynamic allocation of the data, called the moving home. We proposed some rules for the moving home[9]. In this paper, we applied these rules to our MORPG system and evaluated them.

Flash movie authoring environment based on state diagram

A tool for authoring interactive Flash movies is presented. Characters that play in a movie are modeled as object definitions in terms of state-transition diagrams. Each state has a picture and activities. The picture represents appearance of the character in that state. The activities can be selected out of a set of performances such as relocation of the character and generation of other characters. A transition is conditioned in terms of events such as mouse click and collision with other characters. The graphical editor of state-transition diagrams built in this tool is so easy to manipulate that even children can compose interactive Flash animations including video games.

Dynamic reallocation rules on multi-server web-based MORPG system

The web-based-application user base has witnessed rapid growth. It has become necessary to develop techniques that enable systems to manage simultaneous access by a large number of users. We focus on web-based MultiPlayer Online Role-Playing Games (MORPGs), which must be able to cope with a large number of users and a high frequency of user requests. In our previous work, we introduced a system using multiple web servers and a dynamic data allocation method, which is able to manage dynamic change in user requests. Using this method, we achieved a capacity of 320 users, as opposed to the user capacity of 200 for single-server MORPG system. However, we found some cases in which our method was not effective. In this paper, we propose three rules for dynamic data allocation to address different situations. Our evaluation shows that the cache works effectively if the most avatars gather in a certain place.

Prototyping Tool for Web-Based Multiuser Online Role-Playing Game

This letter proposes a prototyping tool for Web-based Multiuser Online Role-Playing Game (MORPG). The design goal is to make this tool simple and powerful. The tool is comprised of a GUI editor, a translator and a runtime environment. The GUI editor is used to edit state-transition diagrams, each of which defines the behavior of the fictional characters. The state-transition diagrams are translated into C program codes, which plays the role of a game engine in RPG system. The runtime environment includes PHP, JavaScript with Ajax and HTML. So the prototype system can be played on the usual Web browser, such as Firefox, Safari and IE. On a click or key press by a player, the Web browser sends it to the Web server to reflect its consequence on the screens which other players are looking at. Prospected users of this tool include programming novices and schoolchildren. The knowledge or skill of any specific programming languages is not required to create state-transition diagrams. Its structure is not only suitable for the definition of a character behavior but also intuitive to help novices understand. Therefore, the users can easily create Web-based MORPG system with the tool.

Easy creation of network-based interactive animations using Islay

This paper describes an implementation of our tool for authoring network-based interactive animations. The tool is named Islay. The interactive animation addressed in this paper is one of computer animations whose scenario is varied according to key and mouse inputs by viewers. An animation made by the tool is constructed as a collection of characters. The behavior of a character is defined by a state-transition diagram. The GUI editor makes it possible to create a simple animation by mouse manipulation within half a minute, if the prepared pictures are used. The animation interpreter in the tool serves multi viewers who operate each network-connected computer. The core routine of the interpreter runs on each viewers computer in this case. The communication between the computers is implemented using our software DSM (distributed shared memory) library. This paper shows the implementation details of the interpreter, as well as the brief overview of the rest of the tool.

A Protocol for Peer-to-Peer Multi-Player Networked Virtual Ball Game

This paper reports our study of how to gain consistency of states in a ball-game typed Distributed Virtual Environment (DVE) with lag, in peer-to-peer (P2P) architecture. That is, we are studying how to reduce in real-time the difference of states between the participating terminals in a virtual ball game caused by transmission lag or update interval. We are also studying how to control shared objects in real-time in a server-less network architecture. Specifically, a priority field called Allocated Topographical Zone (AtoZ) is used in P2P for DVE. By implementing this function, each terminal can compute which avatar holds the ownership of a shared object by calculating mutually the state of the local avatar predicted by the remote terminals. The region for ownership determined by AtoZ allows an avatar to access and control an object dominantly, so that a geometrical property is dynamically changed depending upon the relative arrangement between the object and avatars. Moreover considering the critical case, defined as inconsistent phenomena between the peers, caused by the network latency, a stricter ownership determination algorithm, called dead zone is introduced. By using these protocols in combination, a robust and effective scheme is achieved for a virtual ball game. As an example of the application, a real-time networked doubles air-hockey is implemented for evaluation of the influence of these protocols on interactivity and on consistency.

Relationship between network latency and information quality in a synchronized distributed virtual environment

In this paper, the theoretical modeling of interactive performance on a distributed virtual environment (DVE) is carried out. To study the degradation of the information quality caused by the existence of network latency on a simple virtual task model, Markov model is employed. Compared with the numerical simulation, the proposed model can be a good approximation of the simulation results. The results of subjective experiments show that, in average, the accuracy of human foreseeing behavior marked between the score of the first and second order Markov models.

Peer-to-peer networked field-type virtual environment by using AtoZ

This paper aims to study how to gain consistency of the state in a DVE (distributed virtual environment) with lag, under the condition of peer-to-peer architecture. That is, we study how to reduce in real-time the difference of the DVE state between peers caused by transmission lag or update interval, and how to control the shared object in the online field game. Specifically, the priority field called allocated topographical zone (AtoZ) and mutual prediction protocol is used in peer-to-peer DVE. Moreover considering the critical case (the inconsistent phenomena) caused by the network latency between peers, stricter ownership determination algorithm called the dead zone is introduced. Using these three protocols in combination, a robust and effective scheme is realized. As an example of the application using the protocols, a real-time networked air-hockey is implemented for evaluation of the influence on interactivity and consistency.