- Geometric primitive
The term geometric primitive in
computer graphics andCAD systems is used in various senses, with common meaning of atomic geometric objects the system can handle (draw, store). Sometimes thesubroutine s that draw the corresponding objects are called "geometric primitives" as well. The most "primitive" primitives are point and straight line segment, which were all that earlyvector graphics systems had.In
constructive solid geometry , primitives are simple geometric shapes such as a cube, cylinder,sphere , cone, pyramid,torus .Modern
2D computer graphics systems may operate with primitives which are lines (segments of straight lines, circles and more complicated curves), as well as shapes (boxes, arbitrary polygons, circles).A common set of two-dimensional primitives includes lines, points, and
polygon s, although some people prefer to consider triangles 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 asBézier curve s,circle s, etc.) may be considered primitives; in other cases, curves are complex forms created from many straight, primitive shapes.Commonly used geometric primitives include:
* points
* lines andline segment s
* planes
*circle s andellipse s
*triangle s and otherpolygon s
* spline curvesNote that in 3D applications basic geometric shapes and forms are considered to be primitives rather than the above list. Such shapes and forms include:
*
sphere s
*cube s orbox es
*toroid s
* cylinders
*pyramid s
* TeapotsThese are considered to be primitives in 3D modelling because they are the building blocks for many other shapes and forms. A 3D package may also include a list of extended primitives which are more complex shapes that come with the package. For example, a teapot is listed as a primitive in
3D Studio Max .ee also
*
Texture primitive External links
* [http://www.peachpit.com/articles/article.aspx?p=30594&seqNum=5 Peachpit.com Info On 3D Primitives]
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