Class diagram of the framework. A schematic diagram of the principal classes in our framework, illustrating their relationships. Note that only two classes (Image3DUniverse and Content) are essential for instantiating a new 3D scene with objects in it. The Image3DUniverse class represents the 3D scene, ready for user interaction. The Content class wraps data types like image volumes and meshes, each with a set of properties such as color, transparency and a local transformation. arrows indicate class inheritance. n indicates that the class contains numerous references to instances of the other class. 1 indicates that the class contains one reference to the other class.