The swogl.layout.animation package contains some basic interfaces for animations, which are frequently required in an interactive 3D environment. The intention behind the package was to provide a basis for defining own animations, especially in the LayoutManager3D implementations.
As Markus pointed out in http://forum.byte-welt.de/showthread.php?t=2392 , there already exists a framework for animation, interpolation and timing, namely the Java Timing Framework. It provides interfaces which are similar to some of the interfaces in the swogl.layout.animation package, but with a much more sophisticated and mature API.
It should be considered to use the Java Timing Framework for the animation in Swogl. The framework will cover most of the functionality of the current animation package, but in a much more general form. If necessary, “utility classes” that are specific for Swogl (like arrangement interpolators) could be built on top of the existing framework.