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Graphical projection
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Topics 3D projection Anamorphosis Axonometry Computer graphics Computer-aided design Descriptive geometry Engineering drawing Map projection Picture plane Plans (drawings) Projection (linear algebra) Projection plane Projective geometry Stereoscopy Technical drawing True length Vanishing point Video game graphics Viewing frustum
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In descriptive geometry, true length is any distance between points that is not foreshortened by the view type. In a three-dimensional Euclidean space, lines with true length are parallel to the projection plane. For example, in a top view of a pyramid, which is an orthographic projection, 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 of a pyramid. If any face of a pyramid was parallel to the projection plane (for a particular view), all edges would demonstrate true length.

Examples of views in which all edges have true length are nets.

References

1. Manual of Engineering Drawing 2009, ISBN 0750689854, pp. 81–85

Further reading

• Boundy, A.W. (2012) "Engineering Drawing." McGraw–Hill.
• Simmons, C. H., Maguire, D. E., Phelps, N., & Knovel. (2009). "Manual of engineering drawing." Boston, Newnes.

• Descriptive geometry
• Length