CITEC Central Lab Facilities
CITEC
British Flag   German Flag

Virtual Hand / GoGo

Type: Selection
Authors: Anja Philippsen, Kai Mismahl
Supervisors: Nikita Mattar, Thies Pfeiffer

Original Design

The idea of this selection method is to map the position of the user's hand to the virtual reality. As the range which the user is able to reach directly with his arm movement is very restricted, it is proposed to scale the user's armlength by applying a linear mapping and at some point a non-linear mapping to allow the user to grow his arm further than he would be able to in reality. [1]

User Perspective

The user is able to interact with his hand in the virtual reality. This is very close to real world interactions, therefore the interaction technique is intuitive to use.
Moving his hand, the user can change the position of the virtual representation of his hand. Because of the non-linear mapping he can also reach distant objects which actually would be out of his reach. Object selection and manipulation is possible for close objects as well as quite distant objects.

Technical Details

To realize this technique only a tracking device for the hand is used.
It is important, that the transition between the close-interaction-range and the arm-growing-range is gradual. Otherwise the user might have difficulties to reach objects located near the transition point. The point where the linear mapping changes into a non-linear mapping should be around 2/3 of the user's armlength. [1]

Our Realization

User Perspective

In our implementation the user has a hand object which follows the position and orientation of the real hand, or rather the Wii Mote. The color of the hand turnes red when it is currently collided with an object. Pressing a button the user can hold this object and carry it around. Releasing the button places the object at its current position.
As described in "Technical Details" the user can also change the armlength at run time.

Technical Details

We used a tracked Wii Mote as the input device.
Via the tracking balls on the 3D glasses we get the position of the user's head. By adjusting the armlength as described above we also get the usual distance between head and hand. This offset accords to the relative position of the the hand, so that we can correctly compute the hand position relatively to the user, also when he moves a few steps in the cave.
By pressing the Button "B" on the Wii Mote the user can grasp an object the virtual hand is currently collided with. The object follows the hands position and orientation while the button is pressed. Releasing it also releases the object.
To adjust the armlength the user can press the "Down" Button with the hand in its normal position and after that the "Up" Button while streching the arm. The distance between these points is calculated and is saved as the user's armlength.
If you do not stretch the arm completely while pressing "Up", the range you will be able to reach will be much larger.

References

  1. Ivan Pupyrev, Mark Billinghurst, Suzanne Weghorst, Tadao Ichikawa (1996). The Go-Go Interaction Technique: Non-linear Mapping for Direct Manipulation in VR.