Patrick Monsieurs

Objective and subjective evaluation of the influence of small amounts of delay and jitter on a recent first person shooter game

There have been several studies in the past years that investigate the impact of network delay on multi-user applications. Primary examples of these applications are real-time multiplayer games. These studies have shown that high network delays and jitter may indeed influence the players perception of the quality of the game. However, the proposed test values, which are often high, are not always representative for a large percentile of on-line game players. We have therefore investigated the influence of delay and jitter with numbers that are more representative for typical access networks. This in effect allows us to simulate a setup with multiplayer game servers that are located at ISP level and players connected through that ISPs access network. To obtain further true-to-life results, we opted to carry out the test using a recent first person shooter (FPS) game, Unreal Tournament 2003. It can, after all, be expected that this new generation of games has built-in features to diminish the effect of small delay values, given the popularity of playing these games over the Internet. In this paper, we have investigated both subjective perceived quality and objective measurements and will show that both are indeed influenced by even these small delay and jitter values.

Reducing population size while maintaining diversity

This paper presents a technique to drastically reduce the size of a population, while still maintaining sufficient diversity for evolution. An advantage of a reduced population size is the reduced number of fitness evaluations necessary. In domains where calculation of fitness values is expensive, this results in a huge speedup of the search. Additionally, in the experiments performed, smaller populations also resulted in a faster convergence speed towards an optimal solution.

Reducing Bloat in Genetic Programming

In this paper, several techniques will be presented to constrain the growth of solutions that are constructed by genetic programming. The most successful technique imposes a maximum size on the created individuals of the population that depends solely on the size of the best individual of the population. This method will be compared with other methods to reduce bloat, demonstrating that this method reduces bloat significantly better than the other methods.

Hybrid representations to improve both streaming and rendering of dynamic networked virtual environments

In this paper we present a novel combined usage of image-based and geometrical representations in dynamic networked virtual environments. Contrary to other research, the type of applications we focus on rely on a continuous streaming of representation data as the user navigates through the virtual environment. The client has no prior knowledge of the environment that needs to be rendered and the objects in the environment can be dynamic or static. Our first goal is to present the user with a sufficiently realistic view of the virtual world as soon as possible while reducing disturbing scene buildup artifacts as well as guarantee interactive frame rates. We create image-based representations that are more compact to send than geometrical models so the client will sooner be able to render a more satisfactory view than if we would only be using incrementally transmitted models. The image-based models are also used in combination with traditional LoD techniques to speedup rendering while maintaining good display quality, which is our second goal. We also present a grouping strategy to further speedup image-based rendering. Run-time measurements will show the benefit of using our system.

Exploiting Proxy-Based Transcoding to Increase the User Quality of Experience in Networked Applications

In this work we describe how we extended the functionality of our previously introduced application and network aware proxy system with transcoding capabilities. Based on their compound awareness, our proxies devise a strategy for every connected client that intelligently distributes the clients available bandwidth over the different application data streams. The proxies subsequently put each computed bandwidth allocation strategy into effect by managing and transcoding data streams inside the network before they reach the client. We also present results from the integration of our work into an existing networked virtual environment. These results clearly indicate that our intelligent proxy, enhanced with its novel transcoding functionality, can increase the user quality of experience considerably in networked applications

Inductive Verification and Validation of the KULRoT RoboCup Team

As in many multi-agent applications, most RoboCup agents are complex systems, hard to construct and hard to check if they behave as intended. We present a technique to verify multi-agent systems based on inductive reasoning. Induction allows to derive general rules from specific examples (e.g. the inputs and outputs of software systems). Using inductive logic programming, partial declarative specifications of the software can be induced. These rules can be readily interpreted by the designers or users of the software, and can in turn result in changes to the software. The approach outlined was used to test the KULRoT RoboCup simulator team, which is briefly described.

Client-controlled qos management in networked virtual environments

In this paper, we propose an architecture to regulate the bandwidth usage of multimedia streams in networked virtual environments. In this architecture, intelligent proxies are placed in the network. These proxies can transcode incoming streams to lower quality versions of those streams, thereby decreasing network traffic. A network intelligence layer at the receiver controls these transcoders based on the bandwidth the streams consume, and the importance that the receiving application assigns to each stream. To access this latter information, the network intelligence layer provides an interface between the QoS management of the network and the applications interest manager. This interest manager assigns a relative importance to each individual network stream. As a result, the network intelligence layer separates application logic from network QoS management, thereby maximizing its reusability. These concepts were implemented in an existing networked virtual environment framework, and experiments were performed to validate the ideas. The experiments demonstrate that bandwidth allocation can be changed dynamically, based on user interest, thereby maximizing network throughput and quality of experience.

Ray tracing optimization utilizing projective methods

This paper presents new techniques for speeding up the ray tracing algorithm. By projecting the scene to be ray traced onto perpendicular planes, subdividing the planes with a 2D subdivision scheme (regular grid- and quadtree structures) and traversing these projected scenes throughout the subdividing structures, the methods reported upon exploit the advantages of the 3D voxel- and octree-based acceleration techniques, without having their disadvantage of large memory consumption. Utilizing bounding rectangular extents around the primitives constituting the scene, the techniques covered can be beneficial for many different types of primitives to be ray traced. Results given for the regular grid- and quadtree-based techniques illustrate that even on single-processor machines it becomes viable to ray trace complex scenes-we tested the algorithms presented with scenes containing up to one million primitives-in an affordable time (i.e. in the order of minutes rather than hours or days).