Hi, my name is Eric Gonzalez and today i'll be talking about our project: X-Rings
a hand-mounted 360 degree shape display for grasping in virtual reality.
This work was completed at Microsoft Research
with my collaborators Eyal Ofek, Mar Gonzalez-Franco, and Mike Sinclair.
Immersive VR experiences let users pick up and interact with all kinds of virtual objects
that can vary in their shape, size, and function.
While there are now compelling visuals for these grasping interactions,
users' physical immersion remains limited by the fact that the controller
they're interacting with always feels the same.
To enable richer haptic experiences with virtual objects,
researchers have explored a variety of haptic controllers for VR.
These devices usually focus on higher fidelity rendering at the fingertip
or providing kinesthetic feedback for triggering or pinching actions.
One of the key features of any object we interact with, however,
is its overall shape.
Recent work has pushed towards supporting shape output in VR,
such as devices that can stop the user's fingers to create the sense of a rigid surface
and compact pin arrays that can change shape in the user's palm.
These devices support shape output,
but like the previous controllers are always in contact with the hand.
In contrast other systems enable more natural grasping
by allowing the user's fingers to make and break contact with the device.
But typically these systems have more limited shape output.
Our goal in this work is to enable meaningful, dynamic shape output
while still supporting natural whole hand grasping.
Towards this goal we developed X-Rings: a new form of shape display
that mounts to the user's hand and renders graspable objects.
Our main inspiration comes from previous shape displays
which are usually 2D arrays of vertically actuated pins.
To better support the rendering of fully graspable objects
we aim to replicate this in the radial dimension so the pins extrude outward rather than up.
I'll now highlight some of the key features of X-Rings before reviewing our design principles
and device evaluation.
We designed X-Rings as a stack of four independent motor-controlled expandable rings.
Each ring can change its diameter between 5.7 and 7.7 centimeters
and support up to 15 newtons of applied force.
X-Rings mounts to the user's hand using a Velcro strap across the knuckles
allowing the user to freely grasp and release the rendered shapes.
This lets the manipulation of felt objects feel natural and intuitive.
Since changing shape takes less than 100 milliseconds,
X-Rings can rapidly update as the user moves between different interactable objects.
This fast rendering speed also allows X-Rings to output dynamically changing shapes in real time.
Through capacitive sensing on the device's finger rests
X-Rings can also determine whether or not someone is grasping the device
Allowing us to use touch as an input method and render corresponding grasp animations.
Current sensing through each motor gives the system a sense of how much force is being applied by the user on each ring.
This lets us render objects that can deform or break in response to applied forces.
The goal of our design was to generate shapes that could be naturally grasped by the user's hand.
In our development we noted that many commonly grasped objects
such as cups and tool handles
naturally have a rough radial symmetry to them.
We therefore decided to focus on symmetric radial expansion, where a stack of expanding layers can create full 3D shapes.
This has the added benefit of reducing the system's degrees of freedom
requiring only a single actuator per layer.
The shape change mechanism used by each layer of X-Rings consists of a cam plate with spiral channels.
Each spiral drives a pin radially inward and outward as the cam rotates.
The cam is driven by a bevel gear fixed to the top of the plate.
A small DC motor drives a pinion, causing the gear to rotate and thus the arms to move.
The base of each layer is fixed to the controller handle which straps to the user's hand.
A Vive tracker mounted below the layers allows for spatial tracking in VR.
We also include a 3D printed mockup of a touchpad and buttons above the layers
to demonstrate how future iterations might incorporate traditional controller inputs
within the current form factor.
Further technical details about our implementation and integration with VR applications can be found in our paper.
We also performed a user study to evaluate how well users associate the shapes rendered by X-Rings
with visually presented objects.
In this study, participants would feel a shape rendered on X-Rings without any visual feedback
of the controller or their hand.
From a virtual display of six potential objects
they then selected which object they believed was being rendered.
We tested two rendering conditions
to further explore how physical rendering limitations can impact perception.
In one condition, X-Rings' full 2 cm dynamic range was enabled
while in the other we artificially limited the rendering range to 1 cm
and scaled the output shape accordingly.
Overall users correctly identified the rendered shapes 80% of the time
when rendered with full dynamic range
and 54% of the time when rendered with half dynamic range.
Interaction effects further revealed that certain geometries such as those with subtle features
were more likely to be affected by dynamic range.
These results suggest that radially shape-changing devices can be a suitable approach to rendering graspable objects
but the device's dynamic range can significantly impact users perception of those objects.
While X-Rings is a valuable initial prototype we see several opportunities for improvement.
Currently X-Rings is limited in what it can render by its symmetrical expansion.
By exploring other spiral patterns it may be possible to support asymmetric radial
expansion within a similar form factor.
Similarly, high extension ratio mechanisms
such as telescoping components could allow for the device to become more compact.
We also think combining X-Rings with a grasp resizing or retargeting algorithm
will be an important step towards understanding how closely a rendered shape must match a
visually presented object in order to feel compelling.
Lastly adding closed loop force control in each layer
would further increase the degree of interactivity of rendered objects
In summary, X-Rings is the first 360 degree shape display designed to support grasping in VR.
We believe its compact design, sensing capabilities, and support for natural
whole hand interaction make X-Rings a promising tool for enabling richer haptic feedback in VR.
Thank you for your time and please check out our paper to learn more about the project.