I'm trying to use SharedGroup with a modified SceneGraph I had ealier. I created a Link and a SharedGroup node. It compiles fine, but each time I run it I get the following message: java.lang.NullPointerException at javax.media.j3d.CollisionThread.updateCollidableObjects(Compiled Code ) Exception occurred during Behavior execution: java.lang.NullPointerException <snip> Does anyone know what is happening? I set ENABLE_COLLISION_REPORTING on both the SharedGroup and the Link 'cos I thought that was the problem... Thanks, Chris. ===================================================================== To subscribe/unsubscribe, send mail to [EMAIL PROTECTED] Java 3D Home Page: http://java.sun.com/products/java-media/3D/