Chapter 3 Highly Interactive Scalable Online Worlds

Abstract

The arrival, in the past decade, of commercially successful virtual worlds used for online gaming and social interaction has emphasized the need for a concerted research effort in this media. A pressing problem is that of incorporating ever more elaborate gaming scenarios into virtual worlds while ensuring player numbers can be measured in the millions. This problem reaches across a number of research areas in computing science and has already received attention from the research community in its own right. In this chapter, the major problems associated to the provisioning of expected player interaction in large‐scale virtual worlds is described together with how research efforts may tackle such problems. Conclusions are drawn from observations of related work and a number of future challenges highlighted.

Introduction

There are a number of commercial solutions to online gaming within which players may participate in virtual worlds that are persistent in nature. Such games are commonly termed massively multiplayer online role‐playing games (MMORPGs), which is usually shortened to MMOs. Vendors generate revenue from such gaming environments by regular financial subscriptions made by players and/or from the value of virtual world artifacts (e.g., virtual land sales, percentage taken from the interplayer trading of virtual world artifacts, sale of additional vendor‐created virtual world storylines and artifacts). Fundamental to measuring the financial success of such games is the number of players actively participating: the more players there are the higher the financial rewards for a vendor. For example, World of Warcraft has boasted over 10 million subscriptions at its peak (subscriptions are typically $14 per month) [13]. An inability to attract sufficient player numbers leaves such gaming environments unprofitable and ultimately a wasted business venture. Such a waste is significant as the budget for bringing such games to market may be in excess of $10 million [16], with some placing the figure closer to $50 million [110]. In addition, once an online game is up and running, the maintenance costs may require total investment, including startup, of close to $500 million to contemplate competing as a market leader [110]. These are the figures commonly discussed as of 2008; in years to come, one may assume that vendors of such games discuss investment of in excess of $1 billion. These games are expected to become an integral part of many individuals' leisure time. Having only been around for a decade yet attaining a significant business status, the notion of carrying out research into online gaming should be taken seriously by industrialists and academics alike.

As the number of participating players is an indication of financial success, a pressing research problem is the need to provide scalable solutions for MMOs. One may assume that scalability has been achieved as no new players are ever turned away from a commercial MMO. However, scalability should be measured not only by how many players can log into a virtual world, but how many players can interact with each other at any one point in time and what level of interaction is afforded. Presenting the most attractive gaming scenarios via rich interaction provides a competitive edge in MMOs and is one element of online worlds that players will immediately identify as desirable. This is because vendors attempt to immerse players in their online worlds. Such immersion is only achievable by the ability to afford heightened realism via a highly responsive environment together with minimal hindrance to in‐world player interaction.

There is no doubt that existing commercial solutions have achieved success and brought to market a series of excellent products. The purpose of this chapter is not to indicate that their efforts are not admirable, but to indicate that these are the first steps taken in this area and one may assume that significant improvements will be expected in the future. A subset of such improvements will be related to player interaction within a virtual world whilst maintaining scalability. As this is a fundamental challenge in creating MMOs, research efforts are still required in this area.

There are already a number of research efforts addressing scalability and interactivity in MMOs, with a number of academics contributing to ever more appropriate solutions for over 20 years. Early works do address the scalability/interactivity problem and do provide many of the techniques that modern commercial products base their solutions on. More recently works have continued to address scalability and interactivity in the context of MMOs, yet such works appear in a number of different areas of computing science (e.g., graphics, distributed systems, and parallel simulation). As such, the MMO researcher is faced with a wide variety of different approaches and possible solutions. Furthermore, there exists a large body of work conducted that is not achieved in the context of MMOs, but may provide MMO researchers with a valuable resource. In the future, researchers in other fields may recognize the significance their work may have for MMOs and tailor their solutions appropriately.

The aim of this chapter is to provide an introductory text which explores the problems of MMO scalability and to describe research efforts that may be of benefit. This is achieved by first describing the type of gaming scenarios that may occur in MMOs and relating such scenarios to classic problems so far tackled in distributed systems research. Related work is then presented that is directly or indirectly related to MMOs. A series of challenges associated to MMO scalability and interactivity is then presented that are still to be tackled successfully, posing a number of questions that reinforce the difficulty of such challenges. Finally, conclusions are presented with a brief view of what future challenges may hold for the MMO researcher.