Enhancing video game characters with emotion, mood and personality

Robert Schaap

Recently there have been large improvements regarding video games. The advancements in graphics are especially large. Character expression is not getting the attention it deserves to get. Generating interesting and appropriate facial expressions for video game characters is difficult, but it is very important for the overall game-play experience.Adding moods, personality and emotion to video game characters allows people to connect with the characters they are playing with. It allows the players to identify with characters and create a bond with them. On the other hand, a character with negative personality traits can cause the player to dislike the character and distance himself from the character. This allows the players to become more easily immersed into the game.

Most game developers rely heavily on scripting to create the experience they envision. With the expanding scope of current games it becomes more difficult to rely on scripting solely. Game worlds are becoming larger and more complicated. A lot of interaction takes place not just between the players and the game world but also among players and among elements of the game world. Even when we only consider single player games, the game worlds of current games are so vast that it has become very hard to determine when certain events will take place. Even worse, it is often not even possible to anticipate which events will be taking place.


Imagine the situation where the best friend of the player gets shot and right after that something positive happens, so that the latter event would possibly trigger a script for the player to act happy. This would be very awkward and unrealistic since he just lost a good friend. Of course this could be solved with additional scripting, but this clearly does not scale. The scripts will become complicated and still there will always be situations and sequences of events that the developer did not think about. In order to provide players with a more immersed game experience, it is essential that characters show compelling expressions, in particular, facial expressions. As a comparative method, we selected several intense scenes from classic movies and investigated what would be necessary in order to have a virtual character reenact those scenes inside a video game. We came up with a novel approach that represents the internal state of video game characters by using a PAD-based model which encompasses emotion, mood and personality, and is able to handle the impact on the character of many relevant environment influences. In addition, this internal state representation enables us to easily blend together animations to create lively facial expressions.


For evaluation purposes we have created a questionnaire that evaluates separate aspects of our model. We have evaluated the influence of noise, mood, personality and environment. The way we evaluate these influences is by showing movies of the same scene to the participants. In this movie the screen is split in two parts as can be seen in the figure below. For the two parts we alter certain parameters that correspond to these technique we want to evaluate. These movies are shown to the participants, after which they are asked to answer some questions about them.


We conclude that the approach is quite successful in noticeably improving the consistency of the mood of the characters based on their personality, thus making their behavior more plausible, convincing and interesting. Therefore, we believe the outcome of this research gives a moderate but clear step towards the ultimate goal of creating video game characters who are more realistic on an emotional level.



  • Schaap R and Bidarra R (2008) Towards emotional characters in computer games. In: Entertainment Computing – ICEC 2008 , Stevens SM and Saldamarco SJ (Eds.), LNCS 5309, Springer, ISBN 978-3-540-89221-2, pp. 167-172 (special issue: Proceedings of the International Conference on Entertainment Computing, 25-27 September, Pittsburgh, PA)