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Representing Flow
Colin Ware
UNH
We can do better than this
2D vector fields
Vector components Direction Magnitude
Orientation
Vector sign bit
2D Flow visualization• A landmark study
- Image courtesy of Dr.Laidlaw et al.
OrientDirectionMagnitude
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
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
movement
form
colordifferences
elementsof form
elementsof movement
colorcolor
1
2&3
4A4B
4C5
6
corti
cal la
yers
Contour finding mechanisms
A single column in V1
Theory of contour finding
Field HayesHess
The next stage – rapid propagation
WeakestContour Signal
Strongest ContourSignal
Prediction
2D Flow visualization• A landmark study
- Image courtesy of Dr.Laidlaw et al.
OrientDirectionMagnitude
How to add VSB?
TerminationsSome neurons respond only with terminations in the receptive field.
Asymmetry along path
Halle’s “little stroaks”
Halle, 1868
Fowler and Ware (1988)
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.
A real challenge
Many sliders