The PSS Page
The Personal Space Station Page
Ergonomic Desktop Virtual Reality |
Contents
The driving vision behind the Personal Space Station is a computer
generated interactive 3D workspace designed for a user who is
studying a three-dimensional structure.
Consider the scenario as illustrated in the figure below.
On a desktop is a 3D workspace which displays an image of a
molecular structure.
A comfortably seated head tracked user
has a stereoscopic view of the structure.
Tangible input devices allow the user to interact
with the model of the structure:
to change its position, scale, and orientation;
to select and edit elements;
and to perform measurements within the structure.
The visual and interaction spaces co-located; i.e.
the structure is percieved in the same physical position
as where the user interacts.
Two handed co-located interaction is used to study a molecule.
In this example, the molecule is drawn as a ball-stick and solvent
surface representations.
A cube is used for positioning the molecule,
while a pen is used to position and orient a cutting
plane through the solvent surface.
The cube is held in the non-dominate hand, which acts as a
frame of reference for more precise tasks performed by
the dominate hand.
Key technical notions in this vision are:
-
high quality computer graphics displays:
high resolution, perspectively correct
stereo images are displayed in real time.
-
natural and direct 3D input :
co-located,
two-handed interaction is
available through wireless tangible devices.
The figure shows a schematic diagram of the PSS prototype implementation.
A head tracked user is seated in front of a mirror on which
stereoscopic images of the virtual world are displayed.
The mirror reflects the display surface of the CRT monitor
into a virtual focus plane (VFP) in front of the user.
Cameras track all user actions under the monitor.
In this way the visual and interaction space coincide:
the user reaches under the mirror into the virtual world without
obscuring the image or colliding with the monitor.
A schematic diagram (left) and prototype (right) of the PSS.
The mirror can be mounted
at different orientations in the chassis.
Head tracking is realized by an acoustic tracker or by using two webcams.
Input devices equipped with small markers are tracking
by two progressive scan cameras.
Optical tracking algorithms analyze the camera images
to reconstruct the 3D pose of the devices.
The system is responsive.
The acoustic tracker tracks the head position at approximately 50 Hz.
The optical tracker tracks the devices at approximately 55 Hz.
Typical end-to-end latencies of the optical tracker are around 20 ms.
A cube and a pen as tangible input devices (left). The optical tracker
reconstructs the pose of a device by searching for marker patterns (right).
In summary, the main advantages of the PSS are:
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Bright stereoscopic images under normal office lighting conditions.
Head tracking allows for perspectively correct images to be drawn.
In addition, head tracking provides motion parallax.
-
Users are comfortably seated with their elbows rested on the desktop,
reducing fatigue when performing precise interaction.
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Interaction is within arms reach and co-located, exploiting proprioception
and hand-eye coordination.
-
Input devices are tangible and wireless.
Interaction is two handed, allowing the relative position of hands
to be used as kinesthetic reference frames.
Molecular Graphics
still under construction....
Visual Molecular Dynamics (VMD) is a desktop visualization
package for interactive visualization of molecular structures
such as proteins, nucleic acids and lipids.
The package is widely used in research community for the analysis
of these structures.
VMD has been ported to the PSS.
Two handed PSS-VMD interaction tasks with tangible devices:
molecule positioning and measuring distances between atoms (left)
and control panel setting (right).
The PSS version of VMD incorporates various novel interface
styles that illustrate the power of the PSS:
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Asymmetric bi-manual 3D interaction:
A cube device is held in one hand to position the molecule,
while a pen is held in the other to select one or
more groups of atoms.
Asymmetric bi-manual input is very powerful mechanism which
can be applied to many applications when precise interaction
is desired.
The non-dominant hand is used to position the object,
while the dominant hand is used to perform an interactive task,
such as atom probing, measuring distances between atoms/groups.
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Tangible control menu:
For control tasks, VMD is originally equipped with a
comprehensive mouse-based user interface with many
pop-up windows containing all kinds of widgets.
In the PSS version of VMD, the interface widgets are
located on the faces of the cube device, while the
pen is used to manipulate them.
The governing idea of the PSS-VMD user interface
is to provide the user with the sensation of "holding
a molecule in the hand".
This is joint work with Arjan Kok at TU/eindhoven.
Medical Visualization
still under construction....
Two handed interaction with the visible woman volumetric dataset:
freely positioning of a volume (left),
positioning a cutting plane (middle) and
real time monitoring of anatomical features (right).
Novel interface styles that illustrate the power of the PSS
in the area of medical visualization:
-
Asymmetric bi-manual 3D interaction:
A cube device is held in one hand to position the volume,
while a pen is held in the other to position a cutting plane.
-
Semi-automatic annotation in 2D:
2D interaction is performed on the cutting plane.
As an example, the pen is used to select a pixel on the cutting plane.
This action invokes a procedure that computes all contours
with the pixel value.
The contours will automatically recomputed and displayed on the plane,
when the pose of the pen is changed.
If the pen is used to select a contour the complete surface
around the contour is computed and displayed.
In this way anatomical features can be interactively explored.
Other 2D annotations on the cutting plane are possible,
such as free hand sketching, or interactive segmentation, etc.
The governing idea of the PSS user interface for medical visualization
is to provide the user with the sensation of "the skull in the hand"
metaphor and using this as a reference frame for more
precise operations performed with the dominate hand.
This is joint work with Arjan Kok at TU/eindhoven.
Astronomy
still under construction....
A 64 million star point cloud.
The governing idea of the PSS user interface for astronomy
is to provide the user with the sensation of "having
a galaxy in his/her hand".
This is joint work with Matthias Hopf at University of Stuttgart.
PSSs have been installed at various Dutch research institutes:
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Department of Mathematics and Computing Science,
Eindhoven University of Technology for research in
virtual reality and scientific visualization
(group Prof. Jack van Wijk).
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Department of Biomedical Engineering
Eindhoven University of Technology for research in
biomedical imaging and modeling
(group
Prof. dr. P.A.J. Hilbers).
-
Department of Industrial Design,
Eindhoven University of Technology for research in
user centered engineering
(group
Prof. Jean-Bernard Martens).
-
Section Computational Science, University of Amsterdam
for the interactive visualization of research in
modeling and simulation of dynamical complex systems
(group Prof. Peter Sloot).
In addition, preperations are underway to install two PSSs at
the Department of Radiology, Academic Hospital Maastricht and one PSS
at the Swamerdam Institute of Life Sciences, University of Amsterdam
for research in cell biology.
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"Personal Space Station"
Jurriaan Mulder, Robert van Liere
Proceedings of VRIC 2002, June 2002.
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"Optical Tracking Using Projective Invariant Marker Pattern
Properties"
Robert van Liere, Jurriaan Mulder
IEEE VR 2003, March 2003.
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"An Affordable Optical Head Tracking System for Desktop VR/AR
Systems"
Jurriaan Mulder, Jack Jansen, Arjen van Rhijn
EGVE 2003, June 2003.
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"Virtual Reality in Biological Microscopic Imaging"
Robert van Liere, W. de Leeuw, J. Mulder, P. Verschure,
A. Visser, E. Manders, R. v Driel
IEEE International Symposium on Biomedical Imaging, June 2002