Chapter6


 * Chapter 6: “Static and Moving Patterns”**

- Early stage: feature abstraction. The visual image is analyzed in terms of primitive elements of form, motion, color and stereoscopic depth. - Next: 2D pattern perception stage: the contours are discovered and the visual world is segmented into distinct regions, based on texture, color, motion and contour. - The structure of objects and scenes are discovered, using information about the connections between component parts, shape from shading information, and so on. - Pattern perception can be thought of as a set of mostly 2D processes occurring between feature analysis and full object perception, although aspects of 3D space perception, such as stereoscopic depth and structure-from-motion, can be considered particular kinds of pattern perception. - Finally, objects and significant patterns are pulled out by attentional processes to meet the needs of the task at hand. - Founded in 1912 by German psychologists. - Group consisted of Max Westheimer, Kurt Koffka and Wolfgang - Gestalt means: pattern in German - Gestalt laws: pattern perception - Rules that describe the way we see patterns in visual displays. - There are 8 Gestalt Laws (discussed below) - Things that are close together are perceptually grouped together. - Slocum (1983) called this the **//spatial concentration principle (//Possible FIB or MC)** - We perceptually group regions of similar element density - The simplest and most powerful way to emphasize the relationships between different data entities is to place them in proximity in a display. - Similar elements tend to group together - Palmer and Rock (1994) argue that connectedness is a fundamental Gestalt organizing principle - Connectedness can be a more powerful grouping principle than proximity, color, size or shape. - Connectedness is applied to the node-link diagram, one of the most common methods to represent relationship between concepts. - We are more likely to construct visual entities out of visual elements that are smooth and continuous, rather than contain abrupt changes in direction. - It is easier to identify the sources and destination of connecting lines if they are smooth and continuous - Principle symmetry creates visual whole - Bilateral symmetry stronger than parallelism - Use symmetry to enable user to extract similarity - A closed contour tends to be seen as an object - Wherever a closed contour is seen, there is a very strong perceptual tendency to divide regions of space into "inside" or "outside" the contour. - A region enclosed by a contour becomes a **//common region//** in the terminology of Palmer (1992). (**Possible MC or FIB)** - Smaller components of a pattern tend to be perceived as objects - A **//figure//** is something object like that is perceived as being in the foreground **(Possible MC or FIB)** - The **//ground//** is whatever lies behind the figure **(Possible MC or FIB**) - A **//contour//** is a continuous perceived boundary between regions of a visual image. **(Possible MC or FIB)** - A contour can be defined by a line, by a boundary between regions of different color, by stereoscopic depth, by motion patterns, or by texture. - An **//Advection Trajectory//** is the path taken by a particle dropped in a flow. **(Possible MC or FIB)** - In order to evaluate any visualization, it is necessary to specify a set of tasks. These are points in a vector or flow field where the vectors have zero magnitude. - Presentation of data is layered form is common in **//geographic information systems (GIS)// (Possible MC or FIB)** - **// Laciness: //** the condition under which people perceive two distinct overlapping layers, as opposed to a single fused composite texture. **(Possible MC or FIB)** - One possible application of transparency in user interfaces is to make pop-up menus transparent so that they do not interfere with information located behind them. - Diagrams contain conventional elements, such as abstract labeling codes that are difficult to learn but formally powerful. - There is a specialized academic field called **//graph drawing//** whose goal is to make graphs that are pleasantly laid out and easy to read. **(Possible MC or FIB**) - The essential characteristic of these diagrams is that they consist of **//nodes//**, representing various kinds of entities, and **//links//**, representing relationships between the entities. **(Possible MC or FIB)** - A circle can represent a ring, a flat disk, a ball, a hole, or the boundary between two objects (a disk in a hole). - A general data model that uses a form of node-link diagram is the **//entity-relationship model.// (Possible MC or FIB)** - In entity relationships, **//modeling entities//** can be objects and parts of objects, or more abstract things such as parts of organizations. - **// Relationships //** are the various kinds of connections that can exist between entities. - Both entities and relationships can have attributes. - ** LOOK AT LEC 5 SLIDE WITH TITLE “GRAMMAR OF NODE LINK DIAGRAMS” ** 1. A closed contour in a node-link diagram generally represents an entity of some kind. It might be part of a body of software, or a person in an organization. 2. The shape of the closed contour is frequently used to represent an entity type (an attribute of the entity). 3. The color of an enclosed region represents an entity type (an attribute). 4. The size of an enclosed region can be used to represent the magnitude of an entity (a scalar attribute). 5. Lines that partition a region within a closed contour can delineate subparts of an entity. This may correspond to a real-world multipart object. 6. Closed-contour regions may be aggregated. The result is readily seen as a composite entity. 7. A number of closed-contour regions within a larger closed contour can represent conceptual containment. 8. Placing closed contours spatially in an ordered sequence can represent conceptual ordering of some kind. 9. A line linking entities represents some kind of relationship between them. 10. A line linking closed contours can have different colors, or other graphical qualities such as waviness. This effectively represents an attribute or type of a relationship. 11. The thickness of a connecting line can be used to represent the magnitude of a relationship (a scalar attribute). 12. A contour can be shaped with tabs and sockets to indicate which components have particular relationships. 13. Proximity of components can represent groups. - Only three basic kinds of graphical marks are common to most maps: areas, line features, and point features - Johnson and Shneiderman (1991) developed a visualization technique they call a **//treemap,//** for displaying information about the tree data structures commonly used in computer science. (**Possible MC or FIB)** - The great advantage of the treemap over conventional tree views is that the amount of information on each branch of the tree can be easily visualized. Because the method is space-filling, it can show quite large trees containing thousands of branches. - The disadvantage is that the hierarchical structure is not as clear as it is in a more conventional tree drawing, which is a specialized form of node-link diagram. (**Possbile Short Answer) last 2 points** - WE can use motion as a display technique to represent data that is either static or dynamic - The limitation on perceived data throughput arises from the amount that a given object can be moved before it becomes confused with another object in the next frame--this is called the **//correspondence problem. (//Possible MC or FIB)** - Perceived motion is highly dependent on its context. - A rectangular frame provides a very strong contextual cue for motion perception. - Frames can be used as an effective device for highlighting local relative motion.
 * Three Stage model of perception: (Possible short answer question)**
 * // Priming //** refers to the fact that once we have seen a pattern, it becomes much easier to identify on subsequent appearance. **(Possible MC or FIB)**
 * GESTALT LAWS (Possible short answer) **
 * Law 1: Proximity **
 * Law 2: Similarity **
 * Law 3: Connectedness **
 * Law 4: Continuity **
 * Law 5: Symmetry **
 * Law 6: Closure **
 * Law 7: Relative Size **
 * Law 8: Figure and Ground **
 * CONTOURS **
 * COMPARING 2D FLOW VISUALIZATION TECHNIQUES **
 * PERCETION OF TRANSPERENCY: OVERLAPPING DATA **
 * THE PERCEPTUAL SYNTAX OF DIAGRAMS **
 * Grammar of Node-Link Diagram **
 * THE GRAMMAR OF MAPS **
 * PATTERNS IN MOTION **
 * MOVING FRAMES **