Interactive 3D Flow Visualization Based on Textures and Geometric Primitives

Abstract

This thesis presents research in the area of flow visualization. The theoretical framework is based on the notion that flow visualization methodology can be classified into four main areas: direct, geometric, texture-based, and feature-based flow visualization. Our work focuses on the direct, geometric, and texture-based categories, with special emphasis on texture-based approaches. After presenting the state-of-the-art, we discuss a technique for resampling of CFD simulation data. The resampling tool addresses both the perceptual problems resulting from a brute force hedgehog visualization and flow field coverage problems. These challenges are handled by giving the user control of the resolution of the resampling grid in object space and giving the user precise control of where to place the vector glyphs. Afterward, we present a novel technique for visualization of unsteady flow on surfaces from computational fluid dynamics. The method generates dense representations of time-dependent vector fields with high spatio-temporal correlation. While the 3D vector fields are associated with arbitrary triangular surface meshes, the generation and advection of texture properties is confined to image space. Frame rates of up to 60 frames per second are realized by exploiting graphics card hardware. We apply this algorithm to unsteady flow on boundary surfaces of, large, complex meshes from computational fluid dynamics composed of more than 200,000 polygons, dynamic meshes with time-dependent geometry and topology, as well as medical data. We also apply texture-based flow visualization techniques to isosurfaces. The result is a combination of two well known scientific visualization techniques, namely iso-surfacing and texture-based flow visualization, into a useful hybrid approach. Next we describe our collection of geometric flow visualization techniques including oriented streamlines, streamlets, a streamrunner tool, streamcomets, and a real-time animated streamline technique. We place special emphasis on necessary measures required in order for geometric techniques to be applicable to real-world data sets. In order to demonstrate the use of all techniques, we apply our direct, geometric, and texture-based flow visualization techniques to investigate swirl and tumble motion, two flow patterns found commonly in computational fluid dynamics (CFD). Our work presents a visual analysis of these motions across three spatial domains: 2D slices, 2.5D surfaces, and 3D.