The most common relationship is a parent-child relationship. A group node can have any number of
children but only one parent. A leaf node can have one parent and no children. The other relationship is
a reference. A reference associates a NodeComponent object with a scene graph Node. NodeComponent
objects define the geometry and appearance attributes used to render the visual objects.
A Java 3D scene graphs is constructed of Node objects in parent-child relationships forming a tree
structure. In a tree structure, one node is the root. Other nodes are accessible following arcs from the
root. The arcs of a tree form no cycles. A scene graph is formed from the trees rooted at the Locale
objects. The NodeComponents and reference arcs are not part of the scene graph tree.
Only one path exists from the root of a tree to each of the leaves; therefore, there is only one path from
the root of a scene graph to each leaf node. The path from the root of a scene graph to a specific leaf
node is the leaf node’s scene graph path. Since a scene graph path leads to exactly one leaf, there is one
scene graph path for each leaf in the scene graph.
Each scene graph path in a Java 3D scene graph completely specifies the state information of its leaf.
State information includes the location, orientation, and size of a visual object. Consequently, the visual
attributes of each visual object depend only on its scene graph path. The Java 3D renderer takes
advantage of this fact and renders the leaves in the order it determines to be most efficient. The Java 3D
programmer normally does not have control over the rendering order of objects2.
Graphic representations of a scene graph can serve as design tool and/or documentation for Java 3D
programs. Scene graphs are drawn using standard graphic symbols as shown in Figure 1-1. Java 3D
programs may have many more objects than those of the scene graph.
To design a Java 3D virtual universe a scene graph is drawn using the standard set of symbols. After the
design is complete, that scene graph drawing is the specification for the program. After the program is
complete, the same scene graph is a concise representation of the program (assuming the specification
was followed). A scene graph drawn from an existing program documents the scene graph the program
creates.
The most common relationship is a parent-child relationship. A group node can have any number ofchildren but only one parent. A leaf node can have one parent and no children. The other relationship isa reference. A reference associates a NodeComponent object with a scene graph Node. NodeComponentobjects define the geometry and appearance attributes used to render the visual objects.A Java 3D scene graphs is constructed of Node objects in parent-child relationships forming a treestructure. In a tree structure, one node is the root. Other nodes are accessible following arcs from theroot. The arcs of a tree form no cycles. A scene graph is formed from the trees rooted at the Localeobjects. The NodeComponents and reference arcs are not part of the scene graph tree.Only one path exists from the root of a tree to each of the leaves; therefore, there is only one path fromthe root of a scene graph to each leaf node. The path from the root of a scene graph to a specific leafnode is the leaf node’s scene graph path. Since a scene graph path leads to exactly one leaf, there is onescene graph path for each leaf in the scene graph.Each scene graph path in a Java 3D scene graph completely specifies the state information of its leaf.State information includes the location, orientation, and size of a visual object. Consequently, the visualattributes of each visual object depend only on its scene graph path. The Java 3D renderer takesadvantage of this fact and renders the leaves in the order it determines to be most efficient. The Java 3Dprogrammer normally does not have control over the rendering order of objects2.Graphic representations of a scene graph can serve as design tool and/or documentation for Java 3Dprograms. Scene graphs are drawn using standard graphic symbols as shown in Figure 1-1. Java 3Dprograms may have many more objects than those of the scene graph.To design a Java 3D virtual universe a scene graph is drawn using the standard set of symbols. After thedesign is complete, that scene graph drawing is the specification for the program. After the program iscomplete, the same scene graph is a concise representation of the program (assuming the specificationwas followed). A scene graph drawn from an existing program documents the scene graph the programcreates.
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