Comp/Phys/Mtsc 715 Patterns, Gestalt, Perceived contours, - PDF document

4/2/2012 Comp/Phys/Mtsc 715 Patterns, Gestalt, Perceived contours, Transparency, Motion, Uncertainty Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 1 CH C/P/M 715, Taylor/Feng, SP09 Example Videos • Vis 2010: Van Pelt: file245-3.avi – Illustrative methods for flow visualization • Vis2010: Tikhonov: file290-2.mov – Proxy-based ambient occlusion and relighting Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 2 CH C/P/M 715, Taylor/Feng, SP09 Patterns • Investigation is often about finding patterns – That were previously unknown, or – That depart from the norm. • Finding such patterns can lead to key insights – One of the most compelling reasons for visualization • Today we look at – What does it take for us to see a group? – How is 2D space divided into distinct regions? – When are patterns recognized as similar? – When do different display elements appear related? Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 3 CH C/P/M 715, Taylor/Feng, SP09 1

4/2/2012 Object Perception Stages • Stage 1: Parallel, fast extraction – Form, motion, texture, color, stereo depth – Contrast sensitivity, edge detection, as studied before Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 4 CH C/P/M 715, Taylor/Feng, SP09 Object Perception Stages • Stage 3: Object Identification – Slower, serial identification of objects within the scene – Comparisons with working memory Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 5 CH C/P/M 715, Taylor/Feng, SP09 Object Perception Stages • Stage 2: Pattern Perception – Contours and boundaries form perceptually distinct regions – We’ll study this “middle ground” today Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 6 CH C/P/M 715, Taylor/Feng, SP09 2

4/2/2012 Object Perception Stages • There is feedback! – Linear model is a simplification – Later stage intentions affect earlier stage responses Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 7 CH C/P/M 715, Taylor/Feng, SP09 Pattern Perception: Gestalt “Laws” • Gestalt = “pattern” – School formed by Max Westheimer, Kurt Koffka, and Wolfgang Kohler • Robust rules easily translate into design principles – * Proximity – * Symmetry – * Continuity (and Connectedness) – * Closure – Similarity * = stronger cues – Relative Size – Figure and Ground Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 8 CH C/P/M 715, Taylor/Feng, SP09 Proximity • Things that are close are grouped together – One of the most powerful perceptual organizing principles • We perceptually group regions of similar density • Design Principle: Place related entities nearby Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 9 CH C/P/M 715, Taylor/Feng, SP09 3

4/2/2012 Symmetry (1/2) • Bilateral symmetry stronger than parallelism • Symmetric shapes seen as more likely Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 10 CH C/P/M 715, Taylor/Feng, SP09 Symmetry (2/2) • Design principle: Make use of symmetry to enable user to extract similarity Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 11 CH C/P/M 715, Taylor/Feng, SP09 Continuity • Good continuity of elements • Easier with smooth curves than abrupt changes • Design Principle: Connector and crossing linear elements should be smooth, without sharp bends Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 12 CH C/P/M 715, Taylor/Feng, SP09 4

4/2/2012 Connectedness • Palmer and Rock (1994) argue that this is more fundamental than continuity • Design principle: Positive and negative statement: – Connecting two objects can group them even when they are not otherwise similar. – Unrelated objects should not be connected, or they will appear to be grouped no matter what. Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 13 CH C/P/M 715, Taylor/Feng, SP09 Closure (1/2) • A closed contour is seen as an object • Perceptual system will close gaps in contours Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 14 CH C/P/M 715, Taylor/Feng, SP09 Closure (2/2) • Contour separates world into “inside” and “outside” – Stronger than proximity – Venn diagrams from set theory – Closure and continuity both help • Closed rectangles strongly segment visual field – Provide frames of reference • Design Principle: – Partial obscuration may be okay – Especially for symmetric objects Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 15 CH C/P/M 715, Taylor/Feng, SP09 5

4/2/2012 Similarity • Color or shape similarity groups by row • Separable dimensions enable alternate perception Integral dimensions form stronger pattern • Design Principle: Items to be grouped should share similar characteristics Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 16 CH C/P/M 715, Taylor/Feng, SP09 Relative Size • The smaller components of a pattern tend to be perceived as the object – Black propeller on white background • Horizontal and vertical tend to be seen as objects • Plays into figure/ground principle • Design principle – Make dots the object rather than “cheese grater” Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 17 CH C/P/M 715, Taylor/Feng, SP09 Figure and Ground • The fundamental perceptual act in object identification according to Gestalt school • What is foreground, what is background? • All other principles help determine this Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 18 CH C/P/M 715, Taylor/Feng, SP09 6

4/2/2012 Figure/Ground Illusions from SPAM Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 19 CH C/P/M 715, Taylor/Feng, SP09 Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 20 CH C/P/M 715, Taylor/Feng, SP09 Contours • Perceived continuous boundary between regions – Line (sharp change on both sides in intensity) – Boundary between regions of two colors – Stereoscopic depth – Patterns of motion – Texture – Illusory (continuity & closure): Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 21 CH C/P/M 715, Taylor/Feng, SP09 7

4/2/2012 When do contours jump gaps? • When a smooth curve can be drawn over gaps – Straight lines are easiest – Quite wiggly is possible • Principle: Line up to jump gaps Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 22 CH C/P/M 715, Taylor/Feng, SP09 Edge Completion 4/3/2012 Gestalt, Visualization in the Sciences UNC-CH C/P/M 715, Taylor/Feng, Contours, Uncertainty SP09 Edge Completion 4/3/2012 Gestalt, Visualization in the Sciences UNC-CH C/P/M 715, Taylor/Feng, Contours, Uncertainty SP09 8

4/2/2012 Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 25 CH C/P/M 715, Taylor/Feng, SP09 Transparency (1/2) • Attempting to present multiple data layers • Many perceptual pitfalls – “WARNING, WARNING, DANGER Will Robinson!” – Different layers interfere with each other to some extent – Sometimes layers will fuse perceptually into one – Patterns similar in color, frequency, motion, etc. interfere more • Design principle: – Make layers differ in at least one significant dimension – Try before you buy Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 26 CH C/P/M 715, Taylor/Feng, SP09 Transparency (2/2) • Need good continuity and correct color relationship • Switch to sparse, distinguishable patterns Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 27 CH C/P/M 715, Taylor/Feng, SP09 9

4/2/2012 Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 28 CH C/P/M 715, Taylor/Feng, SP09 Form and Contour in Motion • Contours can be seen in moving dot fields by motion alone – Rivals static contour detection • Phase of the motion seems most salient – Compared to frequency and amplitude • Patterns of dots moving in synchrony group together • Click for app � • Design Principle: – Consider animation for association of groups – Works great for data-driven spots (even linear motion)! Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 29 CH C/P/M 715, Taylor/Feng, SP09 Frames in Motion • Rectangular frame forms strong context • Groups of dots moving together form frame Visualization in the Sciences UNC- 4/3/2012 Gestalt, Contours, Uncertainty 30 CH C/P/M 715, Taylor/Feng, SP09 10