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

5.3 Visualization nodes and subgraphs
Figure 5.8: This UML class diagram gives an overview of the additional implemented
visualization nodes. The full diagram can be found in figure B.4 and B.5.
is high enough). The slope of the distribution can be modified with the σ-value of
the Gauss set phrase, which accords to the amount of neighboring slices seen. This
principle is outlined in figure 5.9. Figure 5.3.1 illustrates this behavior and figure 5.4
describes the modification of µ and σ with control draggers.
5.3.2 Cash-Flow View
The Cash-Flow views are essentially based on the scene graph shown in figure 4.4.2.
Since each volume field dataset is arranged on the same grid, a constant grid node can
be defined to organize the data. Consequently, a Cash-Flow virtual array used with the
data node is at the number of temporal volumes larger than the array of the grid node
itself. To provide four dimensional support only the offset of the responsible selection
has to be altered. Unfortunately, render nodes provided by the library, did not fit to
the presented data and were occasionally slow since all calculations were performed on
the CPU. That is the reason why only two rendering techniques performed well.
Firstly the rendering of the grid and subparts of the grid in arbitrary order is very
useful to evaluate the alignment of the flow data with the image data. The grid is
rendered with this technique as small green points. Subsequently visualizing subparts
with Cash-Flow is easy since only the increment (inc) value has to be modified. The
view supporting this technique got the name ”grid supporting overview”.
Secondly a velocity field overview with glyphs could be realized with small modifications
of the Cash-Flow glyph render node. The right view rendered in figure 5.5 shows
such a glyph view, using every tenth grid position. The glyphs itself are lines which are
constantly colored from blue to red and a length corresponding to a tenth of the given
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