Jouni Smed

Aspects of networking in multiplayer computer games

Distributed, real‐time multiplayer computer games (MCGs) are in the vanguard of utilizing the networking possibilities. Although related research has been done in military simulations, virtual reality systems, and computer supported cooperative working, the suggested solutions diverge from the problems posed by MCGs. With this in mind, this paper provides a concise overview of four aspects affecting networking in MCGs. First, networking resources (bandwidth, latency, and computational power) set the technical boundaries within which the MCG must operate. Second, distribution concepts encompass communication architectures (peer‐to‐peer, client/server, server‐network), and both data and control architectures (centralized, distributed, replicated). Third, scalability allows the MCG to adapt to the resource changes by parametrization. Finally, security aims at fighting back against cheating and vandalism, which are common in online gaming.

Scheduling Algorithms for Computer-Aided Line Balancing in Printed Circuit Board Assembly.

Generalized flexible flow line (GFFL) is a scheduling environment comprising several machine banks which the products visit in the same order but can skip some machine banks. The type of machines in a bank can differ but they are suitable for performing the same manufacturing tasks. To change one product to another demands a set-up operation of the machine. This paper describes several scheduling algorithms for the GFFL problem. The overall structure of these algorithms is similar, consisting of machine allocation and sequencing phases. The algorithms have been integrated into an interactive production scheduling system for electronics assembly. Sample cases are used to illustrate the operation of the system in practice.

Job grouping in surface mounted component printing

Abstract The arrangement of operations in a production line for mounting the surface components on a printed circuit board is discussed. The production program includes a wide range of different products, which causes frequent set-up operations. The overall efficiency of the production line depends heavily on how the printing operations are organized. Set-ups cause delays which can be cut down by selecting carefully the feeders for the components and by solving a suitable sequence for the products. We describe an integrated production management system for job grouping. The system utilizes approximate algorithms for minimizing the number of component switching instants. A discussion of the exact minimization by using mathematical 0/1 integer programming approach is also given. The revision of the production management system has had a major impact on the productivity, and an increase of ca. 58% in the number of component insertions per hour is observed.

Realizing the bullet time effect in multiplayer games with local perception filters

Local perception filters exploit the limitations of human perception to reduce the effects of network latency in multiplayer computer games. Because they allow temporal distortions in the rendered view, they can be modified to realize the bullet time effect, where a player can get more reaction time by slowing down the surrounding game world. In this paper, we examine the concepts behind local perception filters and extend them to cover artificially increased delays. The presented methods are implemented in a testbench program, which is used to study the usability and limitations of the approach.

Grouping PCBs with Minimum Feeder Changes

In printed circuit board (PCB) assembly, the majority of electronic components are inserted by high-speed placement machines. Although the efficient utilization of the machinery is important for a manufacturer, it is hard to fully realize in high-mix low-volume production environments. On the machine level, the component setup strategy adopted by the manufacturer has a significant impact on the overall production efficiency. Usually, the setup strategy is formulated as a part type grouping problem or a minimum setup problem. In this article, we consider a hybridization of these two problems for the single machine case: The object function to be minimized includes a weighted sum of the number of part type groups (giving the number of setup occasions) and the number of feeder changeovers. We present algorithms for the problem and compare their efficiency.

Realizing bullet time effect in multiplayer games with local perception filters

Local perception filters exploit the limitations of human perception to reduce the effects of network latency in multiplayer computer games. Because they allow temporal distortions in the rendered view, they can be modified to realize bullet time effect, where a player can get more reaction time by slowing down the surrounding game world. In this paper, we examine the concepts behind local perception filters and extend them to cover artificially increased delays. The presented methods are implemented in a testbench program, which is used to study the usability and limitations of the approach.

Networking for Computer Games

Networking has become the main selling point for computer games: commercial games are expected to support multiplaying and the online game sites aim at supporting an ever increasing number of users. At the same time, new game console releases rely heavily on the appeal of online gaming, and a whole new branch of mobile entertainment has emerged with intention to develop distributed multiplayer games for wireless applications. This special issue on “Networking for computer games” focuses on the latest research done on networked computer games and presents five papers exploring different aspects of online multiplayer games. Multiplayer computer games require both consistent and responsive networking. Consistency is important for maintaining a similar set of data for all players, whereas responsiveness requires that updates to the data are done as promptly as possible. These two requirements, however, are often contradictory and solving this consistency– responsiveness dichotomy lies in the heart of real-time interactive networking. In the first paper “Towards an information model of consistency maintenance in distributed interactive applications,” Xin Zhang et al. approach this topic by introducing a framework for analysing the state fidelity of predictive methods. A massively multiplayer game can have tens of thousands simultaneous players from all of over the world, which means that the scalability of the chosen network architecture becomes critical. Moreover, amassivemultiplayer game often requires maintaining a persistent game world, where the game progresses around the clock regardless whether a player takes part in it. The next two papers address this topic. In the second paper “High-level development of multiserver online games,” Frank Glinka et al.describe a middleware system called real-time framework, which aims at raising the level of abstraction for the developer of an online game. In the third paper, “ALVIC versus the Internet: redesigning a networked virtual environment architecture,” Peter Quax et al. present a generic framework for deploying a massive multiplayer online game using the existing Internet resources. Mobile gaming and wireless games require a special attention to maintain a continuous and error-free flow information. In the fourth paper “The playing session: enhanced playability for mobile gamers in massive metaverses,” Stefano Cacciaguerra and Gabriele D’Angelo introduce a mechanism, based on mimicking the player activities, which is capable of controlling the communication even in a case of a network failure. The online game sites aim at providing the players more customized content according to the players preference and playing style. This requires methods for analysing the player behavior, which is also important in detecting players who cheat or otherwise misbehave in the game world. In the fifth paper “Visualization of online-game players based on their action behaviors,” Keita Iizuka and Ruck Thawonmas present an approach for recognizing different player-type clusters by visualizing the players in-game decisions.

Preventing look-ahead cheating with active objects

In a turn-based networked multiplayer computer game, it is possible to cheat by delaying the announcement of ones action for a turn until one has received messages from all the other players. This look-ahead cheating can be prevented with a lockstep protocol, which requires that the player first announces a commitment to an action and later on the action itself, which can be compared with the earlier announced commitment. However, because the lockstep protocol requires separate transmissions for the commitment and the action and a synchronization step before the actions can be announced, it slows down the turns of the game. In this paper, we propose that active objects can be used to prevent look-ahead cheating. Moreover, we can parameterize the probability of catching cheaters: The smaller this probability is, the less bandwidth and transmissions are required. In most cases, the mere threat of getting caught is enough to discourage cheating, and, consequently, this probability can be quite small.