CPSC 533C Static 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

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

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

Connectedness Example

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

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)

Transparency Transparency is perceived only when good continuity and color correspondence exists.

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

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.

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.

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.

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