We are developing graphics systems, image preprocessing methods, and interactive manipulation techniques for a space-filling 3D display using a varifocal mirror principle. Our driving problem is a medical imaging need for presentation of three-dimensional intensity information. The major goal of both the image preprocessing and the interactive manipulation has been to overcome obscuration, which we feel is coming to be recognized as the central problem in any space-filling display. In our system, the preprocessing step highlights important image features such as surfaces. At display time, the object can be dynamically edited and rotated for convenient viewing from various directions. Our particular hardware design allows the 3D display to be constructed as an inexpensive add-on to a standard video graphics system. The interactive rotation and other manipulations are achieved by the standard built-in graphics processor.