CPSC 533CStatic and Moving Patterns

Presented by Ken Deeter

Slides borrowed from Colin Ware’s PPT Slides

Gestalt Laws

• Gestalt = German for “Pattern”

• Laws of “pattern perception”– Proposed mechanisms were wrong– Rules themselves still have value

Proximity

• “Things that are close together are perceptually grouped together”

• Rule: Best way of emphasizing relationships between different data entities is to place them in proximity in a display.

Proximity example

a

x

a

b

Similarity

• Similar elements (shape, color) are grouped together.

• Combine with separable dimensions to assist with visual segmentation.

• Rule: Related visual elements should look similar

Similarity Example

a

a b

Continuity

• People are more likely to construct visual groupings out of elements that are smooth and continuous, rather than ones that contain abrupt changes in direction.

• Implies connectedness, which is stronger than proximity. (pg 207 fig 6.8)

• Rule: use connections to show relations

Continuity Example

a

a b c

Connectedness Example

a b

c d

Symmetry

• Symmetrical elements emphasizes a relationship.

• Possible use: use symmetry in an interface to emphasize similarity (figure 6.11 pg 209)

• Rule: Use symmetry to relate visual elements.

Symmetry Example

Closure

• Humans tend to look for closed contours.• Closed contours segment visual space.

Organizing using these segmented regions is stronger than proximity.

• Common uses are Venn Diagrams or Application Windows

• Rule: Use closed regions to segment visual space, group smaller elements.

Closure Examples

a

a b

Relative Size

• Smaller components of a pattern tend to be perceived as objects.

• See Figure 6.15 pg 212

Figure and Ground

• What is foreground and what is background?

• Combination of other laws to segment image into fg/bg

Contours

• People see contours where they don’t really exist.

• Illusory contour (figure 6.18 pg 215)

a

a

b

Transparency• Transparency is perceived only when good

continuity and color correspondence exists.

a

ab

x

y z

w

Overlap

• Perception of overlapping textures depends on visual interference between two patterns

a

ab

c d

Perceptual Syntax

• Various types of illustrations already contain syntax that uses Gestalt principles to code information.– Node-link graphs (fig 6.29 pg 226)– Geographical Maps (fig 6.30 pg 228)– TreeMap (fig 6.31 pg 229)

Patterns in Motion

• Correspondence problem: for motion to work, humans need to perceive correspondence of visual elements between different frames.– Limit motion of elements

– Differentiate elements using shape/color/orientation

• Done incorrectly, results in “wagon wheel effect”

• Vary attributes to make correlation easier.

a

b

c

a

Form and Contour in Motion

• Visual elements can be classified based on differences in movement, with comparable precision to static attributes.

Moving Frames

• Motion perception highly depend on context.

• Examples:– Synched moving dots (fig

6.34 pg 234)

– Dot in Moving frame: often perceived as dot moving instead of frame moving.

a

a b

a

a b

Causality

• Perception of causality between two movements highly dependent on time between movements.– Some experimental results suggest 160ms as

maximum time for perceiving causality between two motions

• Can use specific motions to encode causal relationships in data.

Causality cont.

a

100 200

50%

100%

Time (msec.)

Direct LaunchingDelayed launchingNo causality

Animate Motion

• Humans are very good at perceiving:– Biological motion– Expressiveness in motion

a

a b