Chapter 4 Vortex detection - Computer Graphics and Visualization

Chapter 1. Introduction
Figure 1.1: Minard’s visualization of Napoleon’s campaign to Russia [Tufte, 1990]
more complex and more accurate models that produce larger and larger data sets,
which have to be visualized.
Therefore, scientific visualization has become necessary for scientists and engineers,
in order to obtain insight in the results of their models and measurements. Images
are much better suited for processing by the human visual system, hence the
well-known proverb “One picture says more than a thousand words” (or numbers in this
case).
1.2 Objectives
The research in this thesis describes the development of techniques to assist the scientific
user in coping with the large amounts and high complexity of the data, by
providing interactive techniques for exploring the data. What the user is usually interested
in, are the characteristic phenomena of the data, so-called features. Examples
of features are vortices, boundary layers, and shock waves. Through these features,
the amount of data and its complexity can be reduced. Therefore, we have developed
techniques which extract features from data sets and visualize them.
One classification for visualization techniques distinguishes between: global techniques,
geometric techniques, and feature-based techniques [Post et al., 1999]. Global
techniques render data directly, without deriving curves or polygons first. Global techniques
include arrow plots, direct volume rendering, and direct surface rendering. An
2