I’m currently working on a simple scene graph implementation in Java, which I will share under a open source license soon. By simple I mean simple. If you are looking for a scene graph for your game, you might want to check out other more elaborate scene graphs made especially for that purpose. The purpose of mine is primarily to model simple kinematic chains like robot manipulators for simulation purposes.
What’s neat about this one is that it uses uses Dual Quaternions instead of homogeneous transformation matrices. On of the benefits of doing so is a increase in performance.
The Dual Quaternion class is basically a Java implementation of the C# code found in this beginners guide to Dual Quaterions.
I got a working prototype up and running, and so far I am very pleased with the result.