[week 6 summaries]
The Importance of Stereo and Eye Coupled Perspective for Eye-Hand Coordination in Fish Tank VR
By conducting an experiment based on Fish Tank VR, the authors tried to investigate the relative importance of stereo and head tracking in visually guided hand movements.
Stereo (S) or stereoscopy is a technique that creates two slightly different images with offsets from viewer’s left and right eye in one scene. By perceiving and then combined in the brain, the viewer gets a sense of 3D illusion depth. A LCD shutter glasses are used to provide stereo display.
Head tracking (HT) technology here is leveraged to perform motion parallax. As we know, objects that are farther in our sight field moves “slower” than those with a closer distance when we move relative to the environment. Since our view point has changed during the movement, the scene has to adapt to the new perspective to present a correct view. The HT is utilized to tracking the position and orientation of eyes for updating the viewpoint-dependent scene.
Evaluation
The way to measure the performance is by conducting Fitts tapping task, from which we can analysis the inter-tap intervals to learn about the objects’ feedback.
Methodology of this varied Fitts tapping task is that, by generating several cylinders with different diameters scattering on the checkerboard, the subject is asked to tap the top of those cylinders one after another; the time course of inter-tap interval is measured as reference for environment adaption. One innovation in this task is that a virtual barrier which blocking part of those cylinders is created to force subject change view point.
A trail is consisted of 13 cylinders. Each cylinder is randomly generated with diameter and in-between distances satisfying pre-defined index of difficulty. A trail sequence consists one home target cylinder to start and 12 other ordered targets. Once the subject taps on the home target, the trial is timed. Each trail falls into one of those four conditions (noHT/noS, noHT/S, HT/noS and HT/S). A trail set is trial sequences that covers all those conditions once. Apart from the practice trails, 5 trial sets are carried out for measurement.
Result
The experiment result suggests that stereo view is more important than eye coupled perspective since the average time reduced is 11% in HT and 33% in stereo viewing. On the other hand, by creating the view-blocking barrier to force head position changing, the effect on HT has been proved to be meaningful.
As another object of this experiment, the improvement over the first few taps was shown not as apparent as expected. The hidden key may be the too short inter-tap interval since the movement is so rapid. Also, the subject may have adapted and re-calibrated their conception through the first unmeasured home target tap.
Though the value of different depth cues depends from case to case, but through this experiment, the findings do gain the reference value for future immersion VR design.
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