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Chapter 5. Interaction with Virtual Crowds for VRET of Agoraphobia 5.4 Automatic Motion Adaptation After having defined the interest points the characters should look at, the original character motion has to be adapted in order for it to perform the gaze motion in a smooth and natural way while keeping a maximum of its original walking motion. The method we use for motion adaptation is very similar to that presented in the previous chapter. However, we modified it for online use. We thus will not go into the details of the method in this chapter, but rather explain the differences with the method presented in the previous chapter. Algorithm 5.1 describes the overall gaze simulation loop. It shows the different steps which are done by our method at each time step and for each character. Algorithm 5.1: Gaze Simulation Loop Data: character id Result: character joints’ position and orientation 1 begin 2 for character id do 3 if not gaze active then 4 check mode 5 set constraint 6 if constraint in field of view then 7 compute duration of movement 8 compute motion adaptation 9 compute percentage of motion adaptation 10 11 12 13 14 15 16 17 18 19 <strong>20</strong> 21 22 23 24 25 68 end else if duration >= max gaze duration then deactivate gaze compute percentage of deactivation else check last constraint update constraint position if constraint in field of view then compute motion adaptation compute percentage of motion adaptation else if duration < min gaze duration then keep previous posture else deactivate gaze
5.4. Automatic Motion Adaptation The main difference with the method proposed in the previous chapter is that this method works online. We have integrated the gaze motion adaptation directly into the crowd simulation animation loop. We thus do not have any a priori knowledge of the duration of an interest point. We therefore do not have a set of pre-determined gaze constraints as in the offline method. This does not have much impact on the spatial resolution but it does on the temporal resolution. The computation of the overall displacement map to be applied to the current character posture remains the same as for the offline method. We thus do not discuss this part of the method in this chapter. However, the computation of the amount of rotation to be applied to each joint at each frame needs to be adapted in order to meet online requirements. These modifications are discussed in the following section. 5.4.1 Temporal Resolution The main problem of not having any a priori knowledge of the constraint durations is that we can not filter out the constraints which last under the minimum gaze duration. We therefore have to deal with this on the fly in order to avoid very small, saccadic movements when a point of interest lasts only a fraction of a second. Whenever a new point of interest is selected, we define the amount of time the character should take to perform the gaze motion, depending on the angle of rotation which has to be done; the larger the angle, the longer it takes to perform the motion. We then simply interpolate at each time step to determine the amount of total rotation which has to be done by each joint. However, the problem which can arise is that the interest point can change or exit the field of view before the gaze motion is finished, i.e. before the joints have attained the final gaze posture. The fact that the motion is not finished is not actually a big problem. However, if this is the case, the gaze duration will necessarily be very small. This induces very unrealistic behaviors where characters perform very small saccadic movements. In order to counter this, we have defined a minimum gaze duration of half a second. If the interest point is deactivated before attaining this minimum duration, we artificially maintain the interest at the previous point of interest. Actually, we maintain the previous character posture until the minimum gaze duration threshold is attained. Another difference in the gaze simulation loop between the offline and online methods is that, in the online method, we adapt each character at the current frame, whereas in the offline method, we adapt each character’s complete animation before going on to the next one. We thus have to keep track of each character’s previous posture in the online method. Moreover, we also need to keep track of the starting posture when initiating gaze deactivation or a change in interest point. Indeed, at each time step, we start from the character’s original walking posture and not from the adapted posture at the previous time step. Finally, the remainder of the temporal resolution stays the same as in the offline method. More specifically, the computation of the different time values for eyes, head, and spine to satisfy the gaze constraints and the desynchronization between these three sets of joints, remains the same. 69
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Simulating Interactions with Virtua
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3.2.4 Scripts . . . . . . . . . . .
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7.3 Experimental Protocol . . . . .
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Résumé La Réalité Virtuelle (RV
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CHAPTER 1 Introduction 1.1 Context
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1.3. Contributions in areas of dail
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1.5. Organization of this Document
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CHAPTER 8 Conclusion In the past de
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8.2. Perspectives and Future Work 8
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APPENDIX A Ethics Commission Reques
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- Cette condition persiste pendant
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laires sur un groupe de personnes s
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Richard G Heimberg, Social Phobia -
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APPENDIX B Fearful Situation Docume
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APPENDIX C List of Abbreviations AS
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APPENDIX D Glossary Acrophobia: acr
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List of Figures LIST OF FIGURES 2.1
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List of Figures 6.3 Results to the
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Bibliography BIBLIOGRAPHY American
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Bibliography Dassault Systèmes. ht
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Bibliography Iscan. http://www.isca
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Bibliography A. Mühlberger, M.J. W
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Bibliography B.O. Rothbaum, L.F. Ho
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WHO. The ICD-10 Classification Of M
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