Master's Thesis - Studierstube Augmented Reality Project - Graz ...

5.2 iMEDgine extensions
which eases the access of the image data itself with variable window and level settings.
Consequently, the image volumes returned by these datasets will already be mapped
correctly by passing the related values continuously.
The flow vector field volumes are finally stored in a number of time steps sized
vector structure as an array of float values. Each field is of constant size and organized
as all rows of a slice subsequently stored for the whole volume.
This enables both
libraries, Cash-Flow and Shallows, to deal with this data according to the additionally
available field width, height and depth information.
5.2.2 Viewer
Viewers represent an essential part of iMEDgine. These are render area widgets which
can be arranged arbitrarily inside tabs and equipped with any kind of visualization.
However, after experimenting with several configurations utilizing even one view (class)
for one visualization a better solution turned out: The development of only two different
kinds of iMEDgine-views was adequate.
The first one uses Cash-Flow, supports its
data-flow architecture and provides its classes (and nodes). The drawback with this
view is, that an intern data-flow between the iMEDgine architecture and the Cash-Flow
data nodes is only possible within the view itself. That means, that the dataset class
has to prepare all Cash-Flow ”Virtual Arrays” 1 in advance before Cash-Flow is able
to deal with them. Furthermore, Cash-Flow is rather designed for the visualization
of different grids than of flow data, so this view class has to administer a parallel
data flow of grid-positions and flow-data positions at the same time. Nevertheless, the
Cash-Flow library proved its value, with some adjustments for global field overview
visualizations and grid supporting views due to its abilities for reconfigurable data
access with configurable selection nodes.
A view to administer different independent hardware accelerated visualization nodes
or arbitrary scene graphs is additional available. The goal is to enable a configuration
not only with c++ code and inevitably recompiling the whole application but with a
separate Open Inventor .iv-file. This allows changes of the scene even during run-time
and arbitrary combinations of visualizations in concurrent views. Moreover handling,
1 ”virtual arrays” are specialized Cash-Flow arrays which define arrays within an actual array in
memory. The interface to these arrays are provided by data access nodes respectively selection nodes.
[Kalkusch2005]
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