Hi Laurent, The AmbientLight is constructed in the DisplayRenderer and added as a child of the root BranchGroup of the scene graph. There is no code in VisAD to delete or modify the AmbientLight. It is possible for appliation code to call the getRoot() method to get a reference to the root, then to delete or modify the AmbientLight. I sincerely doubt that your code or Ugo's does this, so this may be some weird behavior of Java3D in Applets. I can't see any connection to mouse clicks. If you can come up with any more evidence about what is going on, I will look into it. Cheers, Bill On Fri, 2 Sep 2005, Laurent BEIGBEDER wrote: > I have a strange problem on my 3D applet: After a few animation step, > ambiant lights are disabled. > > Does anyone had this problem too and know how to resolve it?