The future of video games lies in Virtual Reality, and this new medium demands greater detail not only in the environments but also in the interactive characters that inhabit them. Our project consists of developing a software framework that aims to incorporate emotions to existing non-player characters to increase its social and emotional presence, improving the immersion achieved in video games. To do so, it provides a range of behaviors that the characters will adopt based mainly on an computational model of emotions. This emotional model modulates the character's behaviour according to the events that are continuously received by the character during execution. In turn, the emotional state at any given moment depends on the emotional tendency or personality that has been defined for the character. The framework, called VR NPC, is implemented as a extension of Behavior Designer and Unity. A preliminary experiment has been conducted on a demonstration scenario which seems to make it clear that players are able to perceive and appreciate such emotions in non-player characters.
There are not many works that study the figure of the non-player character (NPC) in videogames,
with notable exceptions [
OZ Project [
Lit sens [
Finally, we are building on earlier work [
To develop this project we used Scrum, the agile methodology, with sprints of 2 weeks, working over an academic year with 3 major milestones to assess progress.
The tools used in this project are Unity, Behavior Designer [
Behavioral systems usually have these elements in common, which are the ones that we have considered: Scenery or environment, Media (VR, in our case) and NPCs (see Figure 1).
For the VR NPC framework, an architecture with three important parts is used: • Emotional Selector: It connects to the Emotional Controller and chooses the appropriate behavior according to the data received. A new type of Behavior designer sequence nodes have been implemented in order to select the branch of the tree to be executed. • Emotional Controller: It manages the data of each emotion and makes the necessary changes when an Event occurs. It is implemented as a Singleton object, and six MonoBehavior classes model the emotions. • Events: A series of scripts that are executed when certain conditions are met. They have been implemented by means of Behavior Designer conditional nodes and actions, plus some Unity scripts.
To test the framework, it has been used to develop an example scenario in which players must solve an Escape Room with the only help of a robotic NPC whose personality (or emotional tendency) can be chosen at the start. The hypothesis is that the manifestation of emotions, according to the chosen model, will give greater credibility to the character and allow the player to establish stronger bonds with him/her, involving him more in the game (via the so-called social presence) and even achieving a better performance on his part.
An A/B test was carried out with 7 users, dividing the participants into 2 groups, conducting a slightly diferent experiment with each one.
• Group A: This control group had the emotional enhancements applied to the character DEACTIVATED, so it only shows emotions in specific situations, predefined in the game script. In the rest of the cases the character shows a neutral expression, both in his face and in his bodily expressiveness. • Group B: This group had the character emotional enhancements ACTIVATED so when the character react to diferent events that occur in the environment, such as the player dropping an important object on the ground, it always shows relevant emotions.
The responses of both groups to the post-experiment questionnaire are summarised in Table 1.
From what we have been able to see in the results obtained from the test, and ignoring the fact that we do not yet have a large set of testers with which to generalise the results, we can appreciate a significant improvement in the emotional model compared to the unemotional one.
Given this situation, it can be said that the desired objective of increasing the emocional and social presence obtained in the performance of the test in the NPC is getting closer.
Question Players enjoying the game.
Players escaping the room.
Players assisted by the NPC.
NPC’s personalities chosen.
Players identifying NPC’s emotions.
Emotions identified (of 7).
In general, it can be said that this framework has been successfully integrated with the previous work, since it has not caused problems in the actions performed by the NPC in the demo scenario and the whole system has worked normally.
We are able to ofer the community a computational model of emotions for VR characters that players will be able to identify and enjoy.