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3.2 Describing a whole Scene with a DAG

A DAG can be used for describing the structure of a whole scene.

A special type of node exists for this purpose: the scene graph node. It is connected to 3 other nodes: A list of child scene graph nodes, a list containing a transformation group and/or attribute groups, and finally to a list of geometric primitives (please see chapter 6 for more information about the different node types). Transformations accumulate on a path from the root of the scene to a leaf node.

The following example creates a polyline at two different locations, the structure of the resulting scene graph is shown in figure 3.2.

Example 3: (taken from: data/examples/scenenode1.dat (7.40))

line1 = POLYLINE2( ((0,0), (4,0)) );
trans1 = TRNSF3PT( (0,2), (1,2), (0,3) );
node1 = SCENENODE( (), (TRANSFORMS(trans1)), (line1) );
SCENEROOT = SCENENODE( (node1), (), (line1) );

**Figure 3.2:** Simple Scene Graph
$\begin{figure}\centering\includegraphics{graph2.ps} \end{figure}$

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Administrator 2002-01-20