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| Virtual universe |
Represents the whole universe containing all the objects.
The virtual universe serves as the root of the scene graph.
The coordinate system of the virtual universe
is right-handed. The x-axis is positive to the right, y-axis is positive up, and z-axis
is positive toward the viewer, with all units in meters.
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| Locale |
Locale is an object, uniquely connected to a coordinate system.
Each locale object in the virtual universe establishes a virtual world Cartesian
coordinate system. A locale object serves as the reference point for visual objects
in a virtual universe.
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| Node |
Is a data element and is an instance of a Xith3D class.
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| Arc |
Represents two kinds of relationships between the Xith3D instances:
- Parent-child relationship
Group node - Can have any number of children but only one parent.
Leaf node - Can have one parent and no children
- Reference relationship
A reference assiociates a NodeComponent object with a Node.
NodeComponent objects define the geometry and appearance attributes used
to render the visual objects.
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| BranchGroup |
A BranchGroup is the root of a subgraph also called branch graph. Objects of this type
are used to form scene graphs. There are two categories of scene subgraphs:
- View branch graph
Specifies the viewing parameters such as the viewing location and
direction.
- Content branch graph
Specifies the contents of the virtual universe (geometry, appearance,
behaviour, location, sound and lights).
BranchGroup objects can be compiled. Compiling converts the entire branch graph
below the branch group to a more efficient form for the renderer.
A branch graph is called Live when it is inserted into a Locale. Each object
in that branch graph become live.
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| Scene Graph Path |
The path from starting from the BranchGroup (= the root of a scene graph) to
a specific leaf node. The path specifies the state information (location,
orienttaion and size) of the leaf.
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| NodeComponent |
NodeComponent is also called a Reference Object.
A NodeComponent may be referenced by more than one Shape3D Object
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| Transform3D |
Transform3D objects represents transformations of 3D geometry such as translation,
rotation, scaling or a combination of these.
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| Canvas3D |
The Canvas3D is derived from the Canvas class of the Abstract Windowing Toolkit (AWT).
At least one Canvas3D object must be referenced in the viewing branch graph of the scene
graph.
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| TransformGroup |
The TransformGroups are used in the creation of scene graphs. An object of this type
hold geometric transformation such as translation and rotation. It is the
only object that can change the location, orientation or size of a visual object.
TransformGroup
objects use transform matrices to provide their own localised view of this coordinate
system.
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| Vector3f |
It is used to specify three floating-point values. Vector objects are used to specify
translations of geometry.
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| Capabilities of an object |
SceneGraphObject is the superclass of nearly every class used to create a scene graph including Group,
Leaf, and NodeComponent.
When a branch graph is made live or compiled, it is possible to change values of a scene graph object.
The list of parameters than can be accessed, and in which way, is called the capabilities of the object.
For example: to be able to change the color values in a GeometryArray object, its color write capability must be set before it
becomes live, or is compiled (obj.setCapability(GeometryArray.ALLOW_COLOR_WRITE)). Attempting to make a change in a live or compiled
object for which the proper capability is not set results in an exception.
Object inherits capability settings from its ancestor classes: Group and Node.
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| Behaviour |
Behavior is a class for specifying animations of visual objects or interaction with visual objects.
The distinction between animation and interaction is whether the behavior is activated in response to the
passing of time or in response to user activities, respectively.
The behavior can change virtually any attribute (location, orientation, size, color or transparency) of a visual object.
Once a behavior is specified for a visual object, the Xith3D system updates the
position, orientation, color, or other attributes, of the visual object automatically.
Each visual object in the virtual universe can have its own predefined behavior. In fact, a visual object
may have multiple behaviors. To specify a behavior for a visual object, the programmer creates the
objects that specify the behavior, adds the visual object to the scene graph, and makes the appropriate
references among scene graph objects and the behavior objects.
A behavior is only active within a spatial boundary.
This boundary is called a scheduling region. The scheduling bounds for a
behavior are set using the setSchedulingBounds method of the Behavior class.
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