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
Orient
Direction
Magnitude
- Image courtesy of Dr.Laidlaw et al.

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

8. elements
of form
form
1
color
3
2& A
4 B
4
4C
rs
5
e
6
lay
al
tic
or
c
movement
color
color
differences
elements
of movement

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

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

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

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