< Zurück | Inhalt | Weiter >

5.1 Scenegraph compilation

The Java 3D system supports the concept of a “compiled” scenegraph. Compilation is typically carried out after the scenegraph structure has been built, but before it is displayed. During compilation Java 3D analyzes the elements in the scenegraph, as well as the scenegraph structure, and attempts to perform optimizations to improve rendering time and scenegraph traversal.


Java 3D uses the capability bits that have been set on the scenegraph elements to identify which optimizations can be applied to the scenegraph. The capability bits that have been set for an object defines a contract between you (the application developer) and the Java 3D system. If, for example, you have not set the ALLOW_TRANSFORM_WRITE capability on a TransformGroup, the Java 3D system could use the fact that the 4 × 4 transformation matrix within the TransformGroup remains constant to optimize rendering.


The use of capability bits is a powerful mechanism for adding complex optimizations in future versions of Java 3D. At present two main scenegraph optimizations have been implemented: attribute merging/sorting and geometry merging.


To take advantage of the benefits of compilation, you must override some of the default settings of the

Shape3D−derived objects in your scenegraph. In particular, the pickable property is set by default for

Shape3D objects; objects with the pickable property will not be optimized during the compile process.


 

5.1.1 Appearance merging and sorting
5.1.2 Geometry merging