Kjetil Raaen | Kristiania University College (original) (raw)
Papers by Kjetil Raaen
Proceedings of the 7th International Conference on Multimedia Systems - MMSys '16, 2016
Lecture Notes in Computer Science, 2015
Virtual Reality(VR) systems have the potential to revolutionise how we interact with computers. H... more Virtual Reality(VR) systems have the potential to revolutionise how we interact with computers. However motion sickness and discomfort are currently severely impeding the adoption. Traditionally the focus of optimising VR systems have been on frame-rate. Delay and frame-rate are however not equivalent. Latency may occur in several steps in image processing, and a frame-rate measure only picks up some of them. We have made an experimental setup to physically measure the actual delay from the user moves the head until the screen of the VR device is updated. Our results show that while dedicated VRequipment had very low delay, smartphones are in general not ready for VR-applications.
Proceedings of the 6th ACM Multimedia Systems Conference on - MMSys '15, 2015
Lecture Notes in Computer Science, 2015
Lecture Notes in Computer Science, 2014
Video games have proved to be an interesting platform for computer scientists as games demand the... more Video games have proved to be an interesting platform for computer scientists as games demand the latest technology, fast response times and effective utilization of hardware. Finding the right games to perform experiments are however difficult. Some researchers create their own smaller prototype games to test their ideas, without performing tests in larger scale productions, which decreases the practical applicability of the conclusion. An important reason is the lack of suitable games for research. This paper proposes a list of qualities and features required by researchers for a video game to be suitable for computer science research. Further, it evaluates four games with open source code and discuss their usefulness. We also consider the current state of open source games and possibilities for enhanced cooperation between the professional and research communities.
User interactions in interactive applications are time critical operations; late response will de... more User interactions in interactive applications are time critical operations; late response will degrade the experience. Sensitivity to delay does however vary greatly with between games. This paper surveys existing literature on the specifics of this limitation. We find a classification where games are grouped with others of roughly the same requirements. In addition we find some numbers on how long latency is acceptable. These numbers are however inconsistent between studies, indicating inconsistent methodology or insufficient classification of games and interactions. To improve classification, we suggest some changes. In general, research is too sparse to draw any strong or statistically significant conclusions. In some of the most time critical games, latency seems to degrade the experience at about 50 ms.
Lecture Notes in Computer Science, 2014
Cloud computing" is a popular way for application providers to obtain a flexible server and netwo... more Cloud computing" is a popular way for application providers to obtain a flexible server and network infrastructure. Providers deploying applications with tight response time requirements such as games, are reluctant to use clouds. An important reason is the lack of real-time guarantees. This paper evaluates the actual, practical soft real-time CPU performance of current cloud services, with a special focus on online games. To perform this evaluation, we created a small benchmark and calibrated it to take a few milliseconds to run (often referred to as a microbenchmrak). Repeating this benchmark at a high frequency gives an overview of available resources over time. From the experimental results, we find that public cloud services deliver performance mostly within the requirements of popular online games, where Microsoft Azure Virtual machines give a significantly more stable performance than Amazon EC2.
2012 41st International Conference on Parallel Processing Workshops, 2012
Supporting thousands of interacting players in a virtual world poses huge challenges with respect... more Supporting thousands of interacting players in a virtual world poses huge challenges with respect to processing. Existing work that addresses the challenge utilizes a variety of spatial partitioning algorithms to distribute the load. If, however, a large number of players needs to interact tightly across an area of the game world, spatial partitioning cannot subdivide this area without incurring massive communication costs, latency or inconsistency. It is a major challenge of game engines to scale such areas to the largest number of players possible; in a deviation from earlier thinking, parallelism on multi-core architectures is applied to increase scalability. In this paper, we evaluate the design and implementation of our game server architecture, called LEARS, which allows for lock-free parallel processing of a single spatial partition by considering every game cycle an atomic tick. Our prototype is evaluated using traces from live game sessions where we measure the server response time for all objects that need timely updates. We also measure how the response time for the multi-threaded implementation varies with the number of threads used. Our results show that the challenge of scaling up a game-server can be an embarrassingly parallel problem.
Lecture Notes in Computer Science, 2013
This demo shows how a server can process heavy, gameenhancing workloads without sacrificing respo... more This demo shows how a server can process heavy, gameenhancing workloads without sacrificing response time by implementing a highly parallelisable game server architecture. The architecture "LEARS" allows for the utilisation of more processing resources for tasks that will enhance the game experience. Using the A* path-finding algorithm, we demonstrate how the server distributes the resources under different levels of load, and how this impacts the response time for the game-clients. The demo allow the viewers to adjust game parameters such as the number of pathfinding entities, the number of player characters and the number of available threads and observe the impact on response time and CPU utilisation.
2014 13th Annual Workshop on Network and Systems Support for Games, 2014
ABSTRACT In many games, a win or a loss is not only contin- gent on the speedy reaction of the pl... more ABSTRACT In many games, a win or a loss is not only contin- gent on the speedy reaction of the players, but also on how fast the game can react to them. From our ongoing project, we aim to establish perceptual thresholds for visual delays that follow user actions. In this first user study, we eliminated the complexities of a real game and asked participants to adjust the delay between the push of a button and a simple visual presentation. At the most sensitive, our findings reveal that some perceive delays below 40 ms. However, the median threshold suggests that motor- visual delays are more likely than not to go undetected below 51-90 ms. These results will in future investigations be compared to thresholds for more complex visual stimuli, and to thresholds established from different experimental approaches.
2011 10th Annual Workshop on Network and Systems Support for Games, 2011
Games where thousands of players can interact concurrently pose many challenges with regards to t... more Games where thousands of players can interact concurrently pose many challenges with regards to the massive parallelism. Earlier work within the field suggests that this is difficult due to synchronization issues. In this paper, we present an implementation of a game server architecture based on a model that allows for massive parallelism. The system is evaluated using traces from live game sessions that has been scaled up to generate massive workloads. We measure the differences in server response time for all objects that need timely updates. We also measure how the response time for the multithreaded implementation varies with the number of threads used. Our results show that the case of implementing a game-server can actually be highly parallel problem.
Proceedings of the 7th International Conference on Multimedia Systems - MMSys '16, 2016
Lecture Notes in Computer Science, 2015
Virtual Reality(VR) systems have the potential to revolutionise how we interact with computers. H... more Virtual Reality(VR) systems have the potential to revolutionise how we interact with computers. However motion sickness and discomfort are currently severely impeding the adoption. Traditionally the focus of optimising VR systems have been on frame-rate. Delay and frame-rate are however not equivalent. Latency may occur in several steps in image processing, and a frame-rate measure only picks up some of them. We have made an experimental setup to physically measure the actual delay from the user moves the head until the screen of the VR device is updated. Our results show that while dedicated VRequipment had very low delay, smartphones are in general not ready for VR-applications.
Proceedings of the 6th ACM Multimedia Systems Conference on - MMSys '15, 2015
Lecture Notes in Computer Science, 2015
Lecture Notes in Computer Science, 2014
Video games have proved to be an interesting platform for computer scientists as games demand the... more Video games have proved to be an interesting platform for computer scientists as games demand the latest technology, fast response times and effective utilization of hardware. Finding the right games to perform experiments are however difficult. Some researchers create their own smaller prototype games to test their ideas, without performing tests in larger scale productions, which decreases the practical applicability of the conclusion. An important reason is the lack of suitable games for research. This paper proposes a list of qualities and features required by researchers for a video game to be suitable for computer science research. Further, it evaluates four games with open source code and discuss their usefulness. We also consider the current state of open source games and possibilities for enhanced cooperation between the professional and research communities.
User interactions in interactive applications are time critical operations; late response will de... more User interactions in interactive applications are time critical operations; late response will degrade the experience. Sensitivity to delay does however vary greatly with between games. This paper surveys existing literature on the specifics of this limitation. We find a classification where games are grouped with others of roughly the same requirements. In addition we find some numbers on how long latency is acceptable. These numbers are however inconsistent between studies, indicating inconsistent methodology or insufficient classification of games and interactions. To improve classification, we suggest some changes. In general, research is too sparse to draw any strong or statistically significant conclusions. In some of the most time critical games, latency seems to degrade the experience at about 50 ms.
Lecture Notes in Computer Science, 2014
Cloud computing" is a popular way for application providers to obtain a flexible server and netwo... more Cloud computing" is a popular way for application providers to obtain a flexible server and network infrastructure. Providers deploying applications with tight response time requirements such as games, are reluctant to use clouds. An important reason is the lack of real-time guarantees. This paper evaluates the actual, practical soft real-time CPU performance of current cloud services, with a special focus on online games. To perform this evaluation, we created a small benchmark and calibrated it to take a few milliseconds to run (often referred to as a microbenchmrak). Repeating this benchmark at a high frequency gives an overview of available resources over time. From the experimental results, we find that public cloud services deliver performance mostly within the requirements of popular online games, where Microsoft Azure Virtual machines give a significantly more stable performance than Amazon EC2.
2012 41st International Conference on Parallel Processing Workshops, 2012
Supporting thousands of interacting players in a virtual world poses huge challenges with respect... more Supporting thousands of interacting players in a virtual world poses huge challenges with respect to processing. Existing work that addresses the challenge utilizes a variety of spatial partitioning algorithms to distribute the load. If, however, a large number of players needs to interact tightly across an area of the game world, spatial partitioning cannot subdivide this area without incurring massive communication costs, latency or inconsistency. It is a major challenge of game engines to scale such areas to the largest number of players possible; in a deviation from earlier thinking, parallelism on multi-core architectures is applied to increase scalability. In this paper, we evaluate the design and implementation of our game server architecture, called LEARS, which allows for lock-free parallel processing of a single spatial partition by considering every game cycle an atomic tick. Our prototype is evaluated using traces from live game sessions where we measure the server response time for all objects that need timely updates. We also measure how the response time for the multi-threaded implementation varies with the number of threads used. Our results show that the challenge of scaling up a game-server can be an embarrassingly parallel problem.
Lecture Notes in Computer Science, 2013
This demo shows how a server can process heavy, gameenhancing workloads without sacrificing respo... more This demo shows how a server can process heavy, gameenhancing workloads without sacrificing response time by implementing a highly parallelisable game server architecture. The architecture "LEARS" allows for the utilisation of more processing resources for tasks that will enhance the game experience. Using the A* path-finding algorithm, we demonstrate how the server distributes the resources under different levels of load, and how this impacts the response time for the game-clients. The demo allow the viewers to adjust game parameters such as the number of pathfinding entities, the number of player characters and the number of available threads and observe the impact on response time and CPU utilisation.
2014 13th Annual Workshop on Network and Systems Support for Games, 2014
ABSTRACT In many games, a win or a loss is not only contin- gent on the speedy reaction of the pl... more ABSTRACT In many games, a win or a loss is not only contin- gent on the speedy reaction of the players, but also on how fast the game can react to them. From our ongoing project, we aim to establish perceptual thresholds for visual delays that follow user actions. In this first user study, we eliminated the complexities of a real game and asked participants to adjust the delay between the push of a button and a simple visual presentation. At the most sensitive, our findings reveal that some perceive delays below 40 ms. However, the median threshold suggests that motor- visual delays are more likely than not to go undetected below 51-90 ms. These results will in future investigations be compared to thresholds for more complex visual stimuli, and to thresholds established from different experimental approaches.
2011 10th Annual Workshop on Network and Systems Support for Games, 2011
Games where thousands of players can interact concurrently pose many challenges with regards to t... more Games where thousands of players can interact concurrently pose many challenges with regards to the massive parallelism. Earlier work within the field suggests that this is difficult due to synchronization issues. In this paper, we present an implementation of a game server architecture based on a model that allows for massive parallelism. The system is evaluated using traces from live game sessions that has been scaled up to generate massive workloads. We measure the differences in server response time for all objects that need timely updates. We also measure how the response time for the multithreaded implementation varies with the number of threads used. Our results show that the case of implementing a game-server can actually be highly parallel problem.