Editing Vector graphics (section)

==Data model==
{{see also | Geometric primitive}}
The [[Logical schema|logical data model]] of vector graphics is based on the mathematics of [[Analytic geometry|coordinate geometry]], in which shapes are defined as a set of points in a two- or three-dimensional [[cartesian coordinate system]], as ''p'' = (''x, y'') or ''p'' = (''x, y, z''). Because almost all shapes consist of an infinite number of points, the vector model defines a limited set of [[geometric primitive]]s that can be specified using a finite sample of salient points called [[Vertex (computer graphics)|vertices]]. For example, a square can be unambiguously defined by the locations of three of its four corners, from which the software can [[interpolation|interpolate]] the connecting boundary lines and the interior space. Because it is a regular shape, a square could also be defined by the location of one corner, a size (width=height), and a rotation angle.

The fundamental geometric primitives are:
* A single [[Point (geometry)|point]].
* A [[line segment]], defined by two end points, allowing for a simple [[linear interpolation]] of the intervening line.
* A [[polygonal chain]] or polyline, a connected set of line segments, defined by an ordered list of points.
* A [[polygon]], representing a region of space, defined by its boundary, a polyline with coincident starting and ending vertices.

A variety of more complex shapes may be supported:
* [[Parametric equation|Parametric curves]], in which polylines or polygons are augmented with parameters to define a non-linear interpolation between vertices, including [[circular arc]]s, [[Cubic Hermite spline|cubic splines]], [[Catmull–Rom spline]]s, [[Bézier curve]]s and [[bezigon]]s.
* Standard parametric shapes in two or three dimensions, such as [[circle]]s, [[ellipse]]s, [[square]]s, [[superellipse]]s, [[sphere]]s, [[tetrahedron]]s, [[superellipsoid]]s, etc.
* Irregular three-dimensional surfaces and solids, are usually defined as a connected set of polygons (e.g., a [[polygon mesh]]) or as parametric surfaces (e.g., [[NURBS]]).
* [[Fractal]]s, often defined as an [[iterated function system]].

In many vector datasets, each shape can be combined with a set of properties. The most common are visual characteristics, such as color, line weight, or dash pattern. In systems in which shapes represent real-world features, such as GIS and BIM, a variety of attributes of each represented feature can be stored, such as name, age, size, and so on.<ref>[https://saylordotorg.github.io/text_essentials-of-geographic-information-systems/s08-02-vector-data-models.html Vector Data Models] {{Webarchive|url=https://web.archive.org/web/20220411030138/https://saylordotorg.github.io/text_essentials-of-geographic-information-systems/s08-02-vector-data-models.html |date=April 11, 2022 }}, ''Essentials of Geographic Information Systems'', Saylor Academy, 2012</ref>

In some Vector data, especially in GIS, information about [[Geospatial topology|topological relationships]] between objects may be represented in the data model, such as tracking the connections between road segments in a [[transport network]].<ref name="Bolstad">{{cite book |last1=Bolstad |first1=Paul |title=GIS Fundamentals: A First Text on Geographic Information Systems |date=2008 |publisher=Eider Press |page=37 |edition=3rd}}</ref>

If a dataset stored in one vector file format is converted to another file format that supports all the primitive objects used in that particular image, then the conversion can be lossless.