IFIP 2.6 Visual Databases Systems Proc. (Lausanne, Switzerland, March 27-29,1995) 1-10.
HCIL-94-06, CS-TR-3286, CAR-TR-714, ISR-TR-94-46.
This paper discusses the design and implementation of interactive smooth zooming of a starfield display. A starfield display is a two dimensional scatterplot of a multidimensional database where every item from the database is represented as a small colored glyph whose position is determined by its ranking along ordinal attributes of the items laid out on the axes. One way of navigating this visual information is by using a zooming tool to incrementally zoom in on the items by varying the attribute range on either axis independently - such zooming causes the glyphs to move continuously and to grow or shrink. To get a feeling of flying through the data, users should be able to track the motion of each glyph without getting distracted by flicker or large jumps - conditions that necessitate high display refresh rates and closely spaced glyphs on successive frames. Although the use of high-speed hardware can achieve the required visual effect for small databases, the twin software bottlenecks of rapidly accessing display items and constructing a new display image fundamentally retard the refresh rate. Our work explores several methods to overcome these bottlenecks, presents a taxonomy of various zooming methods and introduces a new widget, the zoom bar, that facilitates zooming.