Subtle Cues for VR Movies
Project Team
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Supervision |
Motivation/Goal
One of the problems with storytelling in virtual reality is the freedom of the user to look in any direction, which isn't always intended by the director. In contrast to flat monitor games, locking the view direction in VR is not an option, because it leads to motion-sickness and immersion-breaking.While a movie director knows exactly what the viewer will see, a director of VR stories needs to fight for the user's attention. An unstructured VR story which fails to guide the user, leads to decreased 'story immersion' - the feeling of being a part of the story. So instead of using cuts and camera movement, VR directors need to guide the user with different cues.
Our goal was therefore to develop a system based on subtle color and sound changes to help directors guide the users attention in VR applications.
Approach
Since we wanted to test our system in an interactive story, our first choice for the target device was the HTC Vive, which offers room-scale as well as controllers for both hands.We assumed that subtle cues lead to a higher percentage of story related view direction and therefore subconsiously guide the user. Furthermore, we expected that users with subtle cues are less likely to be hindered, resulting in a smoother progression throughout the story.
In our implementation the strength of the color or sound change is defined by the absolute deviation angle between the current view direction of the user and the target direction (the 3D vector from the user position toward the specified target). Doing this, the environment currently being looked at by the user, gets darker, more desaturated, blurrier and the volume of ambient sound decreases, the greater the deviation angle. Thereby we are able to decrease the salience of story unrelated content and in return increase the user attention towards the story.
Evaluation
We used a between-group design for our experiment with three groups assigned to three different conditions. Condition 1 being no cues, condition 2 being weak cues and condition 3 being strong cues. The adjustments in the strength of the cues for the different conditions was based on a preliminary study.We tested every participant over three different experiments, covering different use-case scenarios. For the first experiment, we designed an interactive story in which the participants had to solve story related problems. This was our main experiment to test the use of subtle cues on a short interactive VR story.
The second experiment took place in a simple environment and the participants had the task to find hidden cats. Our intention with this experiment was to gather more data with a repetitive task.
The last experiment consisted of 30 seconds in the same static environment without any assigned task. This should serve as an instrument to find out whether the subtle cues have an influence on the view direction in absence of salient stimuli.
Conclusion/Outlook
Even though the participants in the cue conditions were not informed about the subtle cues, they were faster in completing the assigned tasks when noticing the cues in comparison to the control group. This demonstrates that users intuitively learn to use the system without further explanation.The focus in future research should lie in comparing subtle cues with other direction systems (e.g. direction arrows) in regard to the ease of use, immersion and effectiveness. Additionally, future implementations could possibly use eye-tracking systems to replace the current head movement based approximation of the view direction. This could further improve the system in itself as well as provide more precise evaluation results.