Flow Like Youve Never Seen It Robert S

Flow Like You've Never Seen It Robert S. Laramee Visual and Interactive Computing Group Department of Computer Science Swansea University R. S. Laramee@swansea. ac. uk Robert S. Laramee r. s. laramee@swansea. ac. uk 1

Overview Flow Visualization with a range of techniques: Introduction to flow visualization Flow data and applications Streamline seeding surfaces versus curves Stream, path, and streak surfaces Surface placement Texture based flow visualization Feature-based flow visualization Conclusions and Acknowledgments Robert S. Laramee r. s. laramee@swansea. ac. uk 2

What is Flow Visualization? A classic topic within scientific visualization The depiction of vector quantities (as opposed to scalar quantities) Applications include: aerodynamics, astronomy, automotive simulation, chemistry, computational fluid dynamics (CFD), engineering, medicine, meteorology, oceanography, physics, turbo-machinery design Challenges: to effectively visualize both magnitude + direction, often simultaneously large data sets time-dependent data What should be visualized? (data filtering/feature extraction) Robert S. Laramee r. s. laramee@swansea. ac. uk 3

What is Flow Visualization? Challenge: to effectively visualize both magnitude + direction often simultaneously magnitude only Robert S. Laramee r. s. laramee@swansea. ac. uk orientation only 4

Flow Visualization Classification 1. 2. direct: overview of vector field, minimal computation, e. g. glyphs, color mapping 3. geometric: a discrete object(s) whose geometry reflects flow characteristics, e. g. streamlines 4. feature-based: both automatic and interactive feature-based techniques, e. g. flow topology texture-based: covers domain with a convolved texture, e. g. , Spot Noise, LIC, ISA, IBFV(S) Robert S. Laramee r. s. laramee@swansea. ac. uk 5

Swirl and Tumble Motion swirl motion: characterized by motion about cylinder -aligned axis more stable (easier) Robert S. Laramee r. s. laramee@swansea. ac. uk tumble motion: characterized by motion about axis orthogonal to cylinder unstable, more difficult

Characteristics of Integral Lines Advantages: Implementation: various easy-toimplement streamline tracing algorithms (integration) Intuitive: interpretation is not difficult Applicability: generally applicable to all vector fields, also in three-dimensions Disadvantages: Perception: too many lines can lead to clutter and visual complexity Perception: depth is difficult to perceive, no well-defined normal vector Seeding: optimal placement is very challenging (unsolved problem) Robert S. Laramee r. s. laramee@swansea. ac. uk 7

Automatic Streamline Seeding Videos Robert S. Laramee r. s. laramee@swansea. ac. uk 8

Stream Surfaces Terminology: Stream surface: a surface that is everywhere tangent to flow Stream surface: the union of stream lines seeded at all points of a curve (the seed curve) Next higher dimensional equivalent to a streamline Unsteady flow can be visualized with a path surface or streak surface Robert S. Laramee r. s. laramee@swansea. ac. uk

Stream Surfaces: Advantages Separates (steady) flow: flow cannot cross surface (stream surfaces only) Perception: Less visual clutter and complexity than many lines/curves Perception: well-defined normal vectors make shading easy, improving depth perception Rendering: surfaces provide more rendering options than lines: e. g. , shading and texturemapping etc. Disadvantages: Construction/Implementation: more complicated algorithms are required to construct integral surfaces Occlusion: multiple surfaces hide one another Placement: placement of surfaces is challenging (video) Robert S. Laramee r. s. laramee@swansea. ac. uk

Constructing Streak Surfaces in 3 D Unsteady Vector Fields (Video) Tony Mc. Loughlin, Robert S. Laramee and Eugene Zhang Robert S. Laramee r. s. laramee@swansea. ac. uk

Stream Surface Placement (Video) Tony Mc. Loughlin, Robert S. Laramee and Eugene Zhang Robert S. Laramee r. s. laramee@swansea. ac. uk

Texture-Based Flow Visualization Texture-based flow visualization Complete coverage Flow features shown Difficult to apply to 3 D Downstream direction shown tumble behavior non-ideal (video) Robert S. Laramee r. s. laramee@swansea. ac. uk

Feature-Based Flow Visualization Feature-Based Visualization Topological skeleton of flow is extracted explicitly Features shown automatically Applicable to 3 D Complete coverage Downstream direction not shown red = saddle blue = sink green = source Robert S. Laramee r. s. laramee@swansea. ac. uk swirl motion: very complex near top of chamber (video)

Acknowledgements Thank you for your attention! Any questions? We thank the following for their help: Nick Croft, Matthew Edmunds, Christoph Garth Edward Grundy, Helwig Hauser Rami Malki, Ian Masters, Tony Mc. Loughlin, Zhenmin Peng Juergen Schneider, Benjamin Spencer Xavier Tricoche, Daniel Weiskopf, Eugene Zhang This work was partially funded by EPSRC EP/F 002335/1 Robert S. Laramee r. s. laramee@swansea. ac. uk