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Sourced from java3d-interest list. Posted by Doug Gehringer of Sun

Making compile() make your scene graph faster

Compiling scene graphs can make certain kinds of scene graphs render much more quickly. To take advantage of compile() your scene graph must: have lots of Shape3Ds which share common attributes and transforms, not have indexed geometry, and not have any capability bits or the "pickablity" flag set.

 

Details

Compilation is a great unfulfilled promise for most Java3d applications today. The promise is much improved performance, but almost no applications are seeing a performance benefit today. The reasons for this are two-fold: compile() only helps certain kinds of scene graphs and the default flag settings prevent compile() from optimizing the scene graph.

Here is how compile() works. Compile implements two optimizations to the scene graph: attribute sorting and shape merging. Attribute sorting looks at the attributes on the Shape3Ds and builds a list of unique appearances. It then replaces the redundant appearances with references to the unique appearances. This minimizes the overhead to changing appearances as the scene graph is displayed.

No compile
Shape Num Shapes Num Tris Shape Rate Triangle Rate
Tetrahedron0.5K 2K4.6K18K
Tetrahedron 1K 4K4.6K19K
Tetrahedron 2K 8K5.0K20K
Tetrahedron 4K16K5.0K20K
Icosahedron0.5K10K3.3K65K
Icosahedron 1K20K3.4K68K
Icosahedron 2K40K3.5K70K
Icosahedron 4K80K3.6K71K

Compile
Shape Num Shapes Num Tris Shape Rate Triangle Rate Compile Time
Tetrahedron 0.5K 2K 30K 125K 0.6
Tetrahedron 1K 4K 60K 250K 2.0
Tetrahedron 2K 8K 120K 500K 8.4
Tetrahedron 4K 16K 230K 920K 30.9
Icosahedron 0.5K 10K 17K 340K 0.7
Icosahedron 1K 20K 22K 440K 2.1
Icosahedron 2K 40K 29K 580K 9.9
Icosahedron 4K 80K 30K 600K 34.9

Note
This document is based on the Java3D 1.1 implementation. The 1.2 implementation will have the the same behavior, but it will probably deliver the same performance without the same restrictions. 1.2 will deliver implement alot of the performance optimizations of compile() without the restrictions on pickablity, and may have a better implementation of compile() as well.

 
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Last Updated: $Date: 2006/04/18 18:20:05 $