The Department of Computer Science at the University of Cyprus cordially invites you to the PhD Defense entitled:

The Simulation of Virtual Crowds and their Contribution to Presence in Immersive Virtual Environments

Speaker: Mr. Marios Kyriakou
Affiliation: University of Cyprus, Cyprus
Category: PhD Defense
Location: Room 148, Faculty of Pure and Applied Sciences (FST-01), 1 University Avenue, 2109 Nicosia, Cyprus (directions)
Date: Thursday, February 27, 2014
Time: 10:00-11:00 EET
Host: Yiorgos Chrysanthou (

In most virtual reality systems there are virtual humans moving and interacting with each other, and the user expects to see them behaving as real people do, without any unusual effects. Designing and developing virtual crowds, in terms of simulation and animation, is still a challenge for researchers. The difficulty lies in the complexity of the overall human behavior. Furthermore, there is not sufficient research that studies how a user is being affected by virtual crowds in an Immersive Virtual Environment (IVE) and what are the main factors, in terms of virtual crowd, that affect the feeling of presence of the user who is immersed in an IVE. This thesis is concerned both with improving the quality of crowds simulation as well as with examining the main behavior characteristics that a believable virtual crowd should have. Our first contribution is a novel approach for the crowd navigation problem. Our method is a data driven technique based on the principles of texture synthesis, where crowd navigation paths are produced based on example data, coming from real-world video footage of people. The simulation of the crowd navigation is not done for each human individually, but whole spatiotemporal areas are being synthesized that may contain several humans inside. This has the possibility of capturing better the interaction between neighboring humans. Assuming that we have a satisfactory method for crowd navigation, we study what other behavioral characteristics should virtual crowds have and how the user’s behavior is being affected by virtual crowds in an IVE. Designing and conducting purpose-developed experiments, we found that facilitating collision avoidance between the user and the virtual crowd does not guarantee that the plausibility of the VR system will be raised or that it will be more pleasing to use. On the contrary, collision avoidance by itself, even if it is a significant factor of lifelikeness of the virtual crowd, could accommodate a feeling of discomfort under certain circumstances. We found that when crowd navigation is accompanied with basic interaction between the user and the virtual crowd, both the plausibility and feeling of comfort in the VR system are increased, enhancing the sense of presence. Numerous immersive VR applications rely on user motivation to be actively involved in the environment. Conducting a second series of experiments, we examined the factors that cause a stronger feeling of presence to the user in a populated IVE and encourage the user to be more active. The results of the experiments show that if the virtual crowd is interacting with the user, then the user tends to intervene more to an incident and have stronger feelings. Another interesting finding is that if the user belongs to a group of virtual people, then the possibility of the user intervening and participating in an incident is raised.

Short Bio:
Marios Kyriakou is a PhD candidate at the Department of Computer Science of the University of Cyprus under the supervision of Dr. Yiorgos Chrysanthou. He completed his undergraduate studies at the Department of Computer Engineering and Informatics of University of Patras in 2003 and he received his MSc in Advanced Information Technologies from the Department of Computer Science of University of Cyprus in 2005.  His research interests include crowd simulation, virtual crowds in immersive and semi-immersive virtual reality systems, focusing on immersed users' experience and their sense of presence.

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