Editing Dimension (section)

==In computer graphics and spatial data==
{{Main | Geometric primitive }}

Several types of digital systems are based on the storage, analysis, and visualization of geometric shapes, including [[Vector graphics editor|illustration software]], [[Computer-aided design]], and [[Geographic information systems]]. Different vector systems use a wide variety of data structures to represent shapes, but almost all are fundamentally based on a set of [[geometric primitive]]s corresponding to the spatial dimensions:<ref>[https://saylordotorg.github.io/text_essentials-of-geographic-information-systems/s08-02-vector-data-models.html Vector Data Models], ''Essentials of Geographic Information Systems'', Saylor Academy, 2012</ref>
* '''Point''' (0-dimensional), a single coordinate in a [[Cartesian coordinate system]].
* '''Line''' or '''Polyline''' (1-dimensional) usually represented as an ordered list of points sampled from a continuous line, whereupon the software is expected to [[Interpolation|interpolate]] the intervening shape of the line as straight- or curved-line segments.
* '''Polygon''' (2-dimensional) usually represented as a line that closes at its endpoints, representing the boundary of a two-dimensional region. The software is expected to use this boundary to partition 2-dimensional space into an interior and exterior.
* '''Surface''' (3-dimensional) represented using a variety of strategies, such as a [[polyhedron]] consisting of connected polygon faces. The software is expected to use this surface to partition 3-dimensional space into an interior and exterior.

Frequently in these systems, especially GIS and [[Cartography]], a representation of a real-world phenomenon may have a different (usually lower) dimension than the phenomenon being represented. For example, a city (a two-dimensional region) may be represented as a point, or a road (a three-dimensional volume of material) may be represented as a line. This ''dimensional generalization'' correlates with tendencies in spatial cognition. For example, asking the distance between two cities presumes a conceptual model of the cities as points, while giving directions involving travel "up," "down," or "along" a road imply a one-dimensional conceptual model. This is frequently done for purposes of data efficiency, visual simplicity, or cognitive efficiency, and is acceptable if the distinction between the representation and the represented is understood but can cause confusion if information users assume that the digital shape is a perfect representation of reality (i.e., believing that roads really are lines).