Science at the Speed of Thought - Ambient Intelligence for Scientific Discovery - page 17

Finally, we use three-dimensional volume renderings to produce views of the
data that show more complete structural information throughout the volume.
We find that volume rendering techniques must be used judiciously and are often
most useful when combined with other techniques. In Fig. 11-d, we combine a
volume rendering of OCM scaffold data with a surface rendering of the same
data. This visualization provides useful verification of the surface derivation
technique.
The user interaction techniques are an extremely important aspect of en-
abling exploration of the data sets. Our approach to user interactions is based
on direct manipulation and navigation of the three-dimensional scene, and on
menus that are presented visually within the immersive environment. Navigation
through the scene is accomplished through user movement within the immersive
environment as well as translations and rotations of a track ball that is part of
a hand-held device (the wand ), which is position-tracked within the immersive
environment. The on-screen menus enable the user to turn on and off various
components of the scene and change transparency/opacity, and to use our inter-
active DSOs, such as the clipWand DSO described above. Figure 12 shows an
example of clipping the data used in previous examples.
Fig. 12. Interactive clipping of scaffold and cell data visualization. A three-dimensional
plane under user control cut data away to expose interior features.
Another interaction technique that is useful during collaborative sessions is
the use of a three-dimensional hand-tracked pointer. This pointer is depicted
as a three-dimensional geometric object in the virtual scene. It is attached to
the position-tracked wand so that it moves with the user's hand. This type of
pointer has proved to be very useful because in the immersive environment, non-
tracked users have slightly different views, so it is dicult to point accurately