We address the problem of interacting with scenes that contain a very large
range of scales. Computer graphics environments normally deal with
only a limited range of orders of magnitude before numerical error and other
anomalies begin to be apparent, and the effects vary widely from
environment to environment. Applications such as astrophysics, where
a single scene could in principle contain visible objects from the
subatomic scale to the intergalactic scale, provide a good proving ground
for the multiple scale problem. In this context, we examine methods
for interacting continuously with simultaneously active astronomical data sets
ranging over 40 or more orders of magnitude. Our approach relies
on utilizing a single scale of order 1.0 for the definition of all data
sets. Where a single object, like a planet or a galaxy, may require
moving in neighborhoods of vastly different scales, we employ
multiple scale representations for the single object; normally, these
are sparse in all but a few neighborhoods. By keying the changes of
scale to the pixel size, we can restrict all data set scaling to
roughly three orders of magnitude. Navigation problems are solved by
designing constraint spaces that adjust properly to the large scale changes,
keeping navigation sensitivity at a relatively constant speed in the
user's screen space.