Conclusion and discussion - The Effect of Avatar Model in Stepping Off a Ledge

In this study, we found that the presence of a self-avatar provides important information in the distance estimation task that people report whether they would step off a visual ledge or not.

When self-avatars are presented to subjects, the maximum heights of the ledge that they step off are significantly lower than when the self-avatars are absent. This result is consistent with our prior study. Also, we found that the form of avatar (either full-avatar or line-avatar) makes no significant difference in such tasks. This finding could imply that, in these affordance

judgments, rich polygonal models are not particularly useful. Thus, our finding is consistent with other studies [Thompson et al., 2004] that perception-action judgments are independent of the quality of computer graphics, while our study was more focused on the form of avatars.

Although, additional study is needed to fully understand the relation between these judgments and computer graphics, it is useful for virtual environment designers to know in what situations high fidelity avatars are needed.

As discovered in Lin’s study [Lin, Rieser, & Bodenheimer, 2015], people’s thresholds in these stepping off ledge tasks in the real world is close to the thresholds of full-avatar condition.

Thus, we can explicitly conclude that, for the immersive virtual environments that are primarily focused on people’s spatial perception, the presence of a self-avatar can greatly improve the fidelity of the IVE. Although implementing a self-avatar would require extra equipment and time, the improvement of user’s performance may be worth the effort. On the other hand, the form of self-avatar is not critical in virtual environment in terms of affecting IVE’s fidelity and user’s performance. Thus, if the authenticity of the graphic is not necessarily high, designers of these virtual environments may prefer to choose a less polygon-rich self-avatar to reduce the cost of developing.

Before our experiment, we assumed that two factors could affect people’s performance in affordance judgment tasks in virtual environment. The first factor we assumed is the fidelity of the avatar, which was eliminated by our result. As in our study, the thresholds of subjects experienced low fidelity line-avatar have no significant differences to the thresholds of high

fidelity full-avatar. The second assumption was that the difference of thresholds between no- avatar condition and full-avatar condition is caused because the self-avatar provides scale information about subject’s own body. This assumption is supported by the results of our line- avatar, due to the fact that the thresholds in these two conditions (line-avatar and full-avatar) are similar; while the thresholds in the conditions with avatar and without avatar are

significantly different. And the most noticeable similarity between these avatars is they were all carefully calibrated to represent subjects’ own body dimension. This assumption needs further investigation. One way of studying this would be to partially scale the self-avatar and analyze subject’s threshold, for example, we could stretch avatars leg length while compress the length of torso so the subject could experience the self-avatar at the same eye height.

We felt it was necessary, as part of our experiment, to provide a virtual mirror in order to help users observing their own models. According to our results, the presence of this virtual mirror may provide additional information to subjects as the thresholds were offset by a small amount, compared with our prior study. This is supported by subjects’ feedback during the experiment, as some of them mentioned they had a better understanding about their self- avatar when looking into the virtual mirror. The effect of virtual mirror is also worth further investigation.

During our pilot study, we ran our experiment in a within subject manner, which was, every subject experienced all three condition. Although the order of conditions for each subject was randomized, the thresholds of three conditions of each subject were relatively close. It is most likely because the subjects studied the virtual environment in their first condition, and used those experiences in the following conditions.

In conclusion, for virtual environment that seek to simulate the scene of the real world, actions and the possibilities of action are important components. Having these affordances and actions match their counterparts in real world would increase the similarity of the virtual environment to the real world. And, our study supports that a size matched self-avatar is critical in increasing this similarity while the form of self-avatar is relatively not important. The reason why the self- avatar has this effect remains unproven.

As our results demonstrated, the fidelity of self-avatars is not critical in affordance judgment tasks, we would infer that it is the scale information that the self-avatar provides that really affects people’s performance. Thus, we believe further investigation should be done in how people perceive this scale information. For example, the difference of people’s affordances when they experience the same self-animated avatar in either a first person perspective view or third person perspective view. In another example, the difference of people’s affordances when they either have normal view of their self-avatar, or only have sight on part of their self-avatar (the other part is rendered invisible). Additionally, as found in our study, a high fidelity self- avatar is not needed in distance estimation tasks, then it is worth further study in what situations a high fidelity self-avatars is required for better performance.

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