Motivation

How much information is in a square meter of terrain? In a square kilometer? Depending how closely one looks, even a small patch of ground has an incredible and daunting level of complexity. Contemporary technology allows us to sample elevation on the surface of the Earth at one-meter increments. One square kilometer of data provides more than a million points of data. Ironically, that very capacity for high-resolution can hinder the viewer from comprehending the greatest trends in the data. Furthermore, rendering out all one million points (besides being computationally problematic) borders on an attempt to attain realism - and the human eye is never more critical than when it sees a representation that is striving to be realistic but, nevertheless, fails.

However, that same, critical eye becomes far more permissive when confronted by artistic renderings. A certain amount of latitude is created in the viewer with artistic renderings of real objects. Human perception cavalierly accepts far rougher approximations and stylizations than would ever be found in reality. An accomplished artist can capture the trends and major features of an object in a few strokes. The viewer is not inundated with a superfluity of visual data. Instead, they are given an effective visual summary of the object - the most critical data concerning the object are communicated in an efficient and powerful manner.

A Turner landscape may be a powerful means to present terrain, but it has a significant weakness. It is impossible for the viewer to change his viewpoint. One cannot enter the painting and look back out - or see one hill in the painting from the top of a neighboring hill. But that ability is one of the greatest devices to fully comprehend a piece of terrain. The ability to interact with the presentation of the terrain - to see it from different viewpoints - greatly increases the viewer's understanding and, from an aesthetic standpoint, appreciation of the terrain. This level of interaction requires that any effort to present terrain data must be couched in an interactive real-time context.

There is more than one way to present terrain that satisfies both the needs for interactivity and the appeal and effect of an artistic rendering style. This paper focuses on one method in particular--a view-independent method. The advantage of this method is that the brunt of the calculation workload is performed once and the results of these computations can be blindly pushed through a real-time graphics pipeline, regardless of view port orientation. As long as the means of accomplishing the artistic rendering style are not particularly troublesome for the graphics pipeline, this can lead to some incredibly high rendering rates.

Researched and written by Sean Curtis with a great deal of help from Pete Shirley and Dave Gallup (August 16, 2004).