geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is c ...

, true length is any distance between points that is not foreshortened by the view type.Manual of Engineering Drawing 2009, , pp. 81–85 In a three-dimensional

Euclidean space Euclidean space is the fundamental space of geometry, intended to represent physical space. Originally, that is, in Euclid's Elements, Euclid's ''Elements'', it was the three-dimensional space of Euclidean geometry, but in modern mathematics ther ...

, lines with true length are

parallel Parallel is a geometric term of location which may refer to: Computing * Parallel algorithm * Parallel computing * Parallel metaheuristic * Parallel (software), a UNIX utility for running programs in parallel * Parallel Sysplex, a cluster of IBM ...

to the

projection plane A projection plane, or plane of projection, is a type of view in which graphical projections from an object intersect.Gary R. Bertoline et al. (2002) ''Technical Graphics Communication''. McGraw–Hill Professional, 2002. , p. 330. Projection plane ...

. For example, in a top view of a

pyramid A pyramid (from el, πυραμίς ') is a structure whose outer surfaces are triangular and converge to a single step at the top, making the shape roughly a pyramid in the geometric sense. The base of a pyramid can be trilateral, quadrilat ...

, which is an

orthographic projection Orthographic projection (also orthogonal projection and analemma) is a means of representing Three-dimensional space, three-dimensional objects in Two-dimensional space, two dimensions. Orthographic projection is a form of parallel projection in ...

, the base edges (which are parallel to the projection plane) have true length, whereas the remaining edges in this view are not true lengths. The same is true with an orthographic

side view Side or Sides may refer to: Geometry * Edge (geometry) of a polygon (two-dimensional shape) * Face (geometry) of a polyhedron (three-dimensional shape) Places * Side (Ainis), a town of Ainis, ancient Thessaly, Greece * Side (Caria), a town of ...

of a pyramid. If any face of a pyramid was parallel to the

(for a particular view), all edges would demonstrate true length. Examples of views in which all edges have true length are nets.

References

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References

Further reading