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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).
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primitives, because every polygon can be constructed from triangles. All other graphic elements are built up from these primitives. In three dimensions, triangles or polygons positioned in three-dimensional space can be used as primitives to model more complex 3D forms. In some cases, curves (such as
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support a basic set of geometric primitives: points, polylines, and polygons, only in two dimensional space and the latter two with only straight line interpolation. TIN data structures for representing terrain surfaces as triangle meshes were also added. Since the mid 1990s, new formats have been
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is a polyline 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. Some data models allow for a single feature to consist of multiple polylines, which could
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property or function of two-dimensional space, affording it a number of data modeling efficiencies over true 3-dimensional objects. A shape of any of these dimensions greater than zero consists of an infinite number of distinct points. Because digital systems are finite, only a sample set of the
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is a set of polygon faces in three-dimensional space that are connected at their edges to completely enclose a volumetric region. In some applications, closure may not be required or may be implied, such as modeling terrain. The software is expected to use this surface to partition 3-dimensional
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Frequently, a representation of the shape 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
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specification. Common geometric primitive extensions include: three-dimensional coordinates for points, lines, and polygons; a fourth "dimension" to represent a measured attribute or time; curved segments in lines and polygons; text annotation as a form of geometry; and polygon meshes for
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the user will start with a cuboid, then use extrusion and other operations to create the model. In this use the primitive is just a convenient starting point, rather than the fundamental unit of modelling.
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the intervening shape of the line between adjacent points in the list as a parametric curve, most commonly a straight line, but other types of curves are frequently available, including
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points in a shape can be stored. Thus, vector data structures typically represent geometric primitives using a strategic sample, organized in structures that facilitate the software
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represents a three-dimensional surface by a connected set of parametric functions, similar to a spline or BĂ©zier curve in two dimensions. The most common structure is the
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surface is often spoken of colloquially as "2 1/2 dimensional," because only the upper surface needs to be represented. Thus, elevation can be conceptualized as a scalar
443:, the interface may present the user with the ability to create primitives which may be further modified by edits. For example, in the practice of
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A 3D package may also include a list of extended primitives which are more complex shapes that come with the package. For example, a
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is a subtype of polyhedron in which all faces must be triangles, the only polygon that will always be planar, including the
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collectively connect to form a single closed boundary, could represent a set of disjoint regions (e.g., the state of
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that draw the corresponding objects are called "geometric primitives" as well. The most "primitive" primitives are
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is a standardized two-dimensional or three-dimensional shape defined by a minimal set of parameters, such as an
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A wide variety of vector data structures and formats have been developed during the history of
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defined by two points at its foci, or three points at its center, vertex, and co-vertex.
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OpenGIS Implementation
Specification for Geographic information - Simple feature access
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developed that extend the range of available primitives, generally standardized by the
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the remainder of the shape at the time of analysis or display, using the algorithms of
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and more complicated curves), as well as shapes (boxes, arbitrary polygons, circles).
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for rendering specific primitives such as lines or triangles, frequently with
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A common set of two-dimensional primitives includes lines, points, and
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173:(0-dimensional), a single location with no height, width, or depth.
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A Conceptual
Framework and Comparison of Spatial Data Models
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that the system can handle (draw, store). Sometimes the
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features consisting of several disconnected points.
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533:21 (4): 66–113. doi:10.3138/D794-N214-221R-23R5.
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352:space into an interior and exterior. A
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590:Peachpit.com Info On 3D Primitives
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18:Primitives (computer graphics)
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379:Non-uniform rational B-spline
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244:Cartesian coordinate system
85:constructive solid geometry
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573:"3d studio primitives"
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463:In graphics hardware
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120:2D computer graphics
439:In CAD software or
58:geometric primitive
543:Vector Data Models
497:2D geometric model
386:Application in GIS
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605:Computer graphics
258:A simple polyline
205:Volumetric region
154:Common primitives
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50:CAD systems
599:Categories
513:References
342:Polyhedron
248:Multipoint
161:dimension
139:triangles
89:geometric
491:See also
467:Various
275:vertices
271:Polyline
135:polygons
97:cylinder
507:Simplex
481:shaders
411:POLYVRT
334:ellipse
299:Polygon
219:terrain
148:circles
128:circles
118:Modern
109:pyramid
453:teapot
305:Hawaii
289:, and
124:curves
101:sphere
52:, and
43:vector
317:torus
315:A 3D
240:Point
223:field
210:solid
184:curve
170:Point
113:torus
74:point
479:and
178:Line
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62:prim
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