1. Representing Flow Colin Ware UNH

2. We can do better than this

4. 2D vector fields Vector components Direction Magnitude Orientation Vector sign bit

5. 2D Flow visualization A landmark study - Image courtesy of Dr.Laidlaw et al. Orient Direction Magnitude

6. Perceptual issues Luminance contrast for detail Red on green is hard to see (illustrate) Natural semantics for signalling “more” Longer Wider More dense More contrasty More vivid The background is critical

7. Particle systems for flow vis. Particles are born (randomly in space) Have a behavior (moving with the flow) They leave a trail (a pathline) Color can change (with speed or age) Width can change (speed or age) Particles die

10. Contour finding mechanisms A single column in V1 Theory of contour finding Field Hayes Hess

11. The next stage – rapid propagation Weakest Contour Signal Strongest Contour Signal Prediction

12. 2D Flow visualization A landmark study - Image courtesy of Dr.Laidlaw et al. Orient Direction Magnitude

14. How to add VSB? Terminations Some neurons respond only with terminations in the receptive field. Asymmetry along path Halle’s “little stroaks” Halle, 1868 Fowler and Ware (1988)

15. Important factors Continuity tangential to flow sream Lightness contrast with background (clarity) Show direction using asymmetry along path Use color width | length | contrast | density for speed, or a combination Add symbols if you like Trace forward and/or backward.

16. A real challenge

17. Many sliders