Eurographics/ IEEE-VGTC Symposium on Visualization (2006) Thomas Ertl, Ken Joy, and Beatriz Santos (Editors) Texture Advection on Stream Surfaces: A Novel Hybrid Visualization Applied to CFD Simulation Results Robert S. Laramee, 1 Christoph Garth, 2 Jürgen Schneider, 3 and Helwig Hauser 1 1 The VRVis Research Center, Vienna, Austria, email: {Laramee,Hauser}@VRVis.at 2 Department of Computer Science, University of Kaiserslautern, Germany, e-mail: garth@informatik.uni-kl.de 3 Department of Advanced Simulation Technologies, AVL, Austria, e-mail: juergen.schneider@avl.com Abstract Stream surfaces are a classic flow visualization technique used to portray the characteristics of vector fields, and texture advection research has made rapid advances in recent years. We present a novel hybrid visualization of texture advection on stream surfaces. This approach conveys properties of the vector field that stream surfaces alone cannot. We apply the visualization technique to various patterns of flow from CFD data important to au- tomotive engine simulation including two patterns of in-cylinder flow (swirl and tumble motion) as well as flow through a cooling jacket. In addition, we explore multiple vector fields defined at the stream surface such as veloc- ity, vorticity, and pressure gradient. The results of our investigation highlight both the strengths and limitations of the hybrid stream surface-texture advection visualization technique and offer new insight to engineers exploring and analyzing their simulations. Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture/Image Generation; I.3.7 [Computer Graphics] Three-Dimensional Graphics and Realism–Color, shading, shadowing, and texture; [Simulation and Modeling]: Simulation Output Analysis 1. Introduction Stream surfaces, introduced by Hultquist [Hul90, Hul92], are a well known technique used to visualize properties of flows. They can circumvent the visual complexity or clut- ter associated with seeding many streamlines. With stream surfaces alone, it is difficult to unambiguously convey the downstream and upstream directions of the flow. Texture ad- vection is another effective flow visualization technique that transports texture properties in the direction of the flow in an animated sequence. Texture advection techniques [JEH02, LvWJH04, WHE01, WEHE02] offer the advantages of be- ing fast and providing complete coverage of the vector field domain. We present a hybrid visualization which combines the strengths of both stream surfaces and texture advection tech- niques. The insight provided by traditional stream surfaces is enhanced with fast texture advection on the surface that conveys the direction of the flow through the use of ani- mated convolution of noise textures. By adding a comple- mentary texture-based algorithm we also capture complete coverage of the flow domain across the stream surface. The hybrid visualization is then used to investigate three impor- tant patterns of flow found in engine simulation data: swirl and tumble motion typical of in-cylinder flow and fluid flow through a cooling jacket. The visual analysis and exploration of the engine simulation data is driven by design goals from an engineering point of view. Applying texture advection to stream surfaces raises both technical and perceptual chal- lenges which we address here. The results of our study high- light both the advantages and limitations of the hybrid vi- sualization approach and provide new insight to those engi- neers investigating the properties of the automotive compo- nents they are analyzing. The rest of this paper is organized as follows: Section 2 presents past research related to both stream surface gen- eration and texture advection approaches on general sur- faces. Our hybrid method is presented in Section 3 including an investigation of the in-cylinder patterns of motion (Sec- tion 3.2) and flow through a cooling jacket (Section 3.3). Both perceptual and technical challenges associated with c  The Eurographics Association 2006.