Hi everyone, my name is Martin Feick, and I am a PhD student at Saarland University and a researcher at DFKI.
Today, I wanna give you a brief overview of our work on visuo-haptic illusions for linear translation and stretching using physical proxies in Virtual Reality.
This work was a collaboration with Niko Kleer, André Zenner, Tony Tang, and Antonio Krüger.
A visuo-haptic illusion can be created by warping the virtual space (in this case the virtual hand) mapping haptic properties of various virtual models onto a single physical proxy.
This creates the illusions of touching different real-world geometries but in fact, the user has only been redirected to a different location on the physical object.
However, the question arises how much discrepancy between the physical and virtual object may be introduced while remaining unnoticed by a user.
Therefore, Tinguy and his colleques investigated how much physical and virtual objects may differ with respect to their width, local orientation and curvature.
They found that we can introduce quite substantial differences not detectable by humans exploiting the visual-dominance phenomenon.
However, in the real-world we do not just grasp objects, right?
In fact, we interact and manipulate them because, usually they are not stiff.
Instead, parts of objects
can be translated, rotated, bent, stretched, twisted, even squeezed and so on.
Replicating these interactions is crucial in order to create compelling VR experiences.
In this work, we only take a look at a subset of object manipulations, namely linear translation and stretching.
which can be found in various situations and domains.
But in the following presentation we will use a concrete example of a virtual DJ desk to illustrate the concept.
Imagine you want to design a VR DJ experience without the need of expensive equipment
including adequate haptic feedback for all the sliders of different length on the virtual DJ desk
which would require a dedicated physical proxy for each virtual slider.
So, there is this 1 to 1 mapping.
To overcome this, we propose the use of visuo-haptic illusions alongside functional physical proxies allowing a single physical proxy to act as a stand-in for multiple virtual objects.
We do so, by applying Control Display ratio manipulations to the virtual slider scaling up or down a user's real-world movement.
We ran a study with 24 participants investigation how much discrepancy between the physical proxy and the virtual object can be used while remaining unnoticed.
In our study, we compared two manipulation techniques, linear translation and stretching at the travel distances of 7 and 14cm.
We used an adaptive interleaved-staircase procedure the determine the conservative detection thresholds for the different conditions.
Participants were instructed to grasp the slider and translate it to a goal position while being exposed to different manipulation factors.
Our results show that we can introduce quite substantial offsets which cannot be detected by a user.
Further, we identified that travel distance significantly affects the detection thresholds showing than smaller distances allow for higher manipulation factors.
Moreover, linear stretching seem to support proprioception leading to significantly lower thresholds than in the translation only condition.
We also observed that there seems to be quite consistent differences in humans' proprioceptive acuity.
And we are cherry picking here,
but for the most part participants either had consistently low thresholds in the different conditions as you can see here
or consistently high thresholds.
To summarize the main findings of our study, we found that travel distance significantly affects how much discrepancy can be introduced.
Next, we identified force as a proprioceptive factor significantly contributing to a semantic violation.
And last but not least, we observed that humans proprioceptive acuity differs
posing an interesting question to future work, whether we need some sort of proprioceptive calibration process.
Going back to the DJ desk example shown at the beginning, we now built a single physical proxy slider providing realistic haptic feedback for various sliders on the virtual DJ desk.
An on-the-fly hand-retargeting technique is used to allow the functional proxy to act as a stand-in for multiple virtual sliders of different lengths on the virtual DJ desk
using the CD ratios determined in our study.
To enable a truly multi-purpose proxy, we use a position log alongside a DC motor allowing the slider to be reset to previous positions of different virtual sliders.
Thank you very much. I am happy to take questions.