Distributed game

Dissertação de mestrado em Engenharia InformáticaThe demand for online games has risen over the years, expanding multiplayer support for new and different game genres. Among them are Massively Multiplayer Online games, one of the most popular and successful game types in the industry. Nowadays, this industry is thriving, evolving alongside technological advancements and producing billions in revenue, making it an economic importance. However, as the complexity of these games grows, so do the challenges they face when constructing them. This dissertation aims to implement a distributed game, through a proof of concept or an existing game, using a distributed architecture to acquire knowledge in the construction of such complex systems and the effort involved in dealing with consistency, maintaining communication infrastructure, and managing data in a distributed way. It is also intended that this project implements multiple mechanisms capable of autonomously helping manage and maintain the correct state of the system. To evaluate the proposed solution, a detailed analysis is carried out with performance benchmark analysis, stress testing, followed by an examination of its security, scalability, and distribution’s resilience. Overall, the present research work allowed for a greater understanding of the technologies and approaches used in constructing a gaming system, establishing a new set of development opportunities to be further investi gated upon the constructed solution.A procura por jogos online aumentou ao longo dos anos, expandindo o suporte multiplayer para novos e diferentes géneros. Entre estes estão os jogos Massively Multiplayer Online, um dos tipos de jogos mais populares e bem-sucedidos na indústria. Atualmente, esta indústria está a prosperar, evoluindo com os avanços tecnológicos e gerando milhares de milhões em receita, tornando-se uma importância económica. Porém, à medida que a complexidade destes jogos aumenta, também aumenta os problemas encontrados durante a sua construção. Esta dissertação tem como objetivo implementar um jogo distribuído, através de uma prova de conceito ou um jogo existente, usando uma arquitetura distribuída a fim de adquirir conhecimento na construção destes sistemas complexos e o esforço envolvido em lidar com consistência, manter a infraestrutura de comunicação e gerir dados de maneira distribuída. Para isto, é pretendido que este projeto também implemente vários mecanismos capazes de, forma autônoma, ajudar a gerir e manter o correto estado do sistema. Para avaliar o solução proposta, uma análise detalhada é realizada sobre o desempenho, segurança, escalabilidade e resiliência da distribuição do sistema. De forma geral, o presente trabalho de pesquisa permitiu uma maior compreensão das tecnologias e abordagens utilizadas na construção de um sistema de jogos, estabelecendo um novo conjunto de oportunidades de desenvolvimento a serem investigadas sobre a solução construída

Yhteneväisyyden ja reagointikyvyn tasapainon tutkiminen verkkomoninpelien yhteneväisyyden ylläpidossa

Multiplayer online gaming has become a massive part of the game industry. Games that use network connections are known to be vulnerable to communication problems like latency, jitter and packet loss. These problems may cause players to suffer from delayed responsiveness or weird game entity behaviors. Games typically fight against network problems by using consistency maintenance methods which need to perform a balancing act between the game's consistency and responsiveness. A huge variety of techniques exists, but there has not been a clear guideline about how a suitable technique should be selected. This Thesis proposes a categorization for the consistency maintenance techniques based on their ability to handle time or data. Categorization is also evaluated with a user study by implementing a single technique from each category and testing them with a simple game. Results from the evaluation are further used to form an analysis for each proposed category. Analysis is used to make small conclusions about the advantages and disadvantages for each category together with a suggestion of how to balance with the consistency-responsiveness ratio to maintain the playability of the game. Pessimistic techniques are considered to provide good consistency in the cost of responsiveness and vice versa for optimistic techniques. PPT is considered as a good solution for a game that does not require real-time simulation, while PDT works well with a game that requires high consistency and may tolerate long response times. OPT is considered as a suitable solution for a game which contains easily predictable shared state entities and ODT is recommended for a game that contains clear decision points.Verkkomoninpelit ovat nousseet massiiviseksi osaksi peliteollisuutta. Verkkoyhteyksiä käyttävät pelit ovat tunnettuja siitä, että ne kärsivät helposti yhteyteen liittyvistä ongelmista kuten viiveestä, yhteyden huojunnasta ja pakettihävikistä. Nämä ongelmat voivat aiheuttaa pelin reagointikyvyn heikkenemistä tai pelissä esiintyvien objetien erikoista käyttäytymistä. Pelit kamppailevat verkon ongelmia vastaan yleensä käyttämällä erilaisia yhteneväisyydenhallintamenetelmiä, jotka tasapainottelevat pelin yhteneväisyyden ja reagointikyvyn välillä. Laaja valikoima erilaisia tekniikoita on jo saatavilla, mutta niiden valintaan liittyvää selkeää ohjeistusta ei ole vielä kehitetty. Tämä työ esittää tavan luokitella yhteneväisyydenhallintatekniikat perustuen niiden kykyyn hallita aikaa tai tietoa. Tuloksena syntyneet kategoriat myös testataan käyttäjätestauksessa pienen pelin avulla, johon toteutetaan yksi tekniikka jokaisesta kategoriasta. Testauksen tuloksista muodostetaan analyysi jokaiselle ehdotetulle kategorialle. Lopuksi analyysiä käytetään esittämään pieniä johtopäätöksiä jokaisen kategorian vahvuuksista ja heikkouksista. Lisäksi esitetään ehdotus siitä, miten yhteneväisyyden ja reagointikyvyn tasapainottelukertoimia on mahdollista hyödyntää pelin pelattavuuden ylläpidossa. Pessimististen tekniikoiden päätellään tuottavan hyvää yhteneväisyyttä alennetun reagointikyvyn kustannuksella, kun taas optimiset tekniikat mahdollistavat nopean reagointikyvyn alennetun yhteneväisyyden kustannuksella. PPT toimii hyvin sellaisten pelien kanssa, jotka eivät vaadi reaaliaikasimulaatiota. PDT puolestaan toimii hyvin niiden pelien kanssa, jotka vaativat korkean yhteneväisyyden ja pystyvät hyväksymään pitkän reagointiajan. OPT toimii hyvin, mikäli pelin jaetun tilan objektit ovat helposti pääteltävissä. ODT:ta puolestaan suositellaan käytettäväksi, kun pelin päätöksentekopisteet ovat helposti määritettävissä

Reducing the effect of network delay on tightly-coupled interaction

Tightly-coupled interaction is shared work in which each person’s actions immediately and continuously influence the actions of others. Tightly-coupled interaction is a hallmark of expert behaviour in face-to-face activity, but becomes extremely difficult to accomplish in distributed groupware. The main cause of this difficulty is network delay – even amounts as small as 100ms – that disrupts people’s ability to synchronize their actions with another person. To reduce the effects of delay on tightly-coupled interaction, I introduce a new technique called Feedback-Feedthrough Synchronization (FFS). FFS causes visual feedback from an action to occur at approximately the same time for both the local and the remote person, preventing one person from getting ahead of the other in the coordinated interaction. I tested the effects of FFS on group performance in several delay conditions, and my study showed that FFS substantially improved users’ performance: accuracy was significantly improved at all levels of delay, and without noticeable increase in perceived effort or frustration. Techniques like FFS that support the requirements of tightly-coupled interaction provide new means for improving the usability of groupware that operates on real-world networks

Effects of Local Latency on Games

Video games are a major type of entertainment for millions of people, and feature a wide variety genres. Many genres of video games require quick reactions, and in these games it is critical for player performance and player experience that the game is responsive. One of the major contributing factors that can make games less responsive is local latency — the total delay between input and a resulting change to the screen. Local latency is produced by a combination of delays from input devices, software processing, and displays. Due to latency, game companies spend considerable time and money play-testing their games to ensure the game is both responsive and that the in-game difficulty is reasonable. Past studies have made it clear that local latency negatively affects both player performance and experience, but there is still little knowledge about local latency’s exact effects on games. In this thesis, we address this problem by providing game designers with more knowledge about local latency’s effects. First, we performed a study to examine latency’s effects on performance and experience for popular pointing input devices used with games. Our results show significant differences between devices based on the task and the amount of latency. We then provide design guidelines based on our findings. Second, we performed a study to understand latency’s effects on ‘atoms’ of interaction in games. The study varied both latency and game speed, and found game speed to affect a task’s sensitivity to latency. Third, we used our findings to build a model to help designers quickly identify latency-sensitive game atoms, thus saving time during play-testing. We built and validated a model that predicts errors rates in a game atom based on latency and game speed. Our work helps game designers by providing new insight into latency’s varied effects and by modelling and predicting those effect

Managing Network Delay for Browser Multiplayer Games

Latency is one of the key performance elements affecting the quality of experience (QoE) in computer games. Latency in the context of games can be defined as the time between the user input and the result on the screen. In order for the QoE to be satisfactory the game needs to be able to react fast enough to player input. In networked multiplayer games, latency is composed of network delay and local delays. Some major sources of network delay are queuing delay and head-of-line (HOL) blocking delay. Network delay in the Internet can be even in the order of seconds. In this thesis we discuss what feasible networking solutions exist for browser multiplayer games. We conduct a literature study to analyze the Differentiated Services architecture, some salient Active Queue Management (AQM) algorithms (RED, PIE, CoDel and FQ-CoDel), the Explicit Congestion Notification (ECN) concept and network protocols for web browser (WebSocket, QUIC and WebRTC). RED, PIE and CoDel as single-queue implementations would be sub-optimal for providing low latency to game traffic. FQ-CoDel is a multi-queue AQM and provides flow separation that is able to prevent queue-building bulk transfers from notably hampering latency-sensitive flows. WebRTC Data-Channel seems promising for games since it can be used for sending arbitrary application data and it can avoid HOL blocking. None of the network protocols, however, provide completely satisfactory support for the transport needs of multiplayer games: WebRTC is not designed for client-server connections, QUIC is not designed for traffic patterns typical for multiplayer games and WebSocket would require parallel connections to mitigate the effects of HOL blocking

"I'm the Jedi!" - A Case Study of User Experience in 3D Tele-immersive Gaming

Abstract—In this paper, we present the results from a quantitative and qualitative study of distributed gaming in 3D tele-immersive (3DTI) environments. We explore the Qual-ity of Experience (QoE) of users in the new cyber-physical gaming environment. Guided by a theoretical QoE model, we conducted a case study and evaluated the impact of various Quality of Service (QoS) metrics (e.g., end-to-end delay, visual quality, etc.) on 3DTI gaming experience. We also identified a number of non-technical factors that are not captured by the original theoretical model, such as age, social interaction, and physical setup. Our analysis highlights new implications for the next-generation gaming system design, as well as a more comprehensive conceptual framework that captures non-technical influences for user experience in such environments

A Network-Agnostic and Cheat-Resistant Framework for Multiplayer Online Games

"Video games are kids' stuff" may be still in the minds of many people. But the video games industry is far beyond its infancy and has already grown into a multi-billion dollar business. The NPD Group reports that in 2007 the revenues generated in the U.S. with video game soft- and hardware for consoles and personal computers reached a total of 18.8 billion dollars, a 40 percent increase over 2006. According to PricewaterhouseCoopers, the global sales will even surpass those of the music industry within the next years. With the success of the Internet, online games are a constantly increasing part of these sales. According to DFC Intelligence, the worldwide online game market will grow to over 13 billion dollars in 2011. The probably most successful online game genre today is that of the so-called Massively Multiplayer Online Games (MMOGs). This kind of games provides vast virtual worlds, where thousands of players can meet and interact simultaneously. Most of these worlds are persistent, i.e. they may be online for years. They are hosted on Internet servers which are online 24/7 and players can join and leave the game whenever they like to. The persistence of the game world allows for long-term development of virtual avatars with individual characteristics and possessions. The leader of the MMOG market today is Blizzard Entertainment with the title World of Warcraft. In the beginning of 2008, World of Warcraft had 10 million subscribers (each paying up to 15 dollars per month) and a market share of 62 percent. Developing todays video games is a complex and cost-intensive task and multiplayer online functionality has a significant share in this. In 2008, the first video game hit the 100 million dollar mark for development costs. In addition to that, publishers of online games need to provide the necessary services to allow their customers to play the game over the Internet. Traditionally, most online games and nearly all MMOGs are built relying on the Client/Server architecture. The client software runs on the player's computers and shows only an audio-visual representation of the game world. It accepts commands issued by the player and transmits them to the server. Processing the commands and managing the state of the game is completely done on the server-side. Thus, to be able to handle hundreds or thousands of players simultaneously, large amounts of computing power and network bandwidth are required. Additionally, the service requires a large staff for server maintenance, software updates, billing and customer services. The provision of the World of Warcraft service did cost about 200 million dollars since its launch in November 2004. In addition to the effort of maintaining a multiplayer online game service after its launch there arises another challenge: keeping the game free of cheaters. A cheater may be defined as a user that performs an action that gives an advantage over his opponents that is considered unfair by the game developer. One must be aware that cheating is a major concern in multiplayer games as it seriously affects the game experience of honest players. Especially for subscription-based online games this is fatal, since customers will cancel their subscriptions if the experience doesn't meet their expectations. Game publishers usually do not hesitate to close the accounts of players that they believe to have cheated. For example, in 2006 Blizzard Entertainment announced in their forums that they have banned 59,000 players from World of Warcraft within a single month

Netcode in modern fighting games.

A lo largo de este trabajo, revisaremos los fundamentos de sistemas de redes y cómo funciona Internet. Analizaremos cómo los juegos comunican datos entre los ordenadores y cómo ha cambiado en este aspecto a lo largo de la historia de los videojuegos, particularmente en los juegos de lucha. Además, recopilaremos una breve historia de los juegos de lucha, y su diseño en relación con los avances en los sistemas de redes. Por último, propondremos un ejemplo básico sobre cómo se podría construir diferentes tipos de códigos de red y cómo funcionan, lo cual nos permitirá ver las ventajas y desventajas de los diferentes métodos. Sobre todo, nos enfocaremos en los códigos de red más significativos de hoy en día: “Rollback” y “Delay-Based” y su evolución en la industria de los juegos de lucha.pre-print2038 K

Characterizing the Effects of Local Latency on Aim Performance in First Person Shooters

Real-time games such as first-person shooters (FPS) are sensitive to even small amounts of lag. The effects of network latency have been studied, but less is known about local latency -- that is, the lag caused by local sources such as input devices, displays, and the application. While local latency is important to gamers, we do not know how it affects aiming performance and whether we can reduce its negative effects. To explore these issues, we tested local latency in a variety of real-world gaming systems and carried out a controlled study focusing on targeting and tracking activities in an FPS game with varying degrees of local latency. In addition, we tested the ability of a lag compensation technique (based on aim assistance) to mitigate the negative effects. To motivate the need for these studies, we also examined how aim in FPS differs from pointing in standard 2D tasks, showing significant differences in performance metrics. Our studies found local latencies in the real-world range from 23 to 243~ms that cause significant and substantial degradation in performance (even for latencies as low as 41~ms). The studies also showed that our compensation technique worked well, reducing the problems caused by lag in the case of targeting, and removing the problem altogether in the case of tracking. Our work shows that local latency is a real and substantial problem -- but game developers can mitigate the problem with appropriate compensation methods