True length
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.
Sources and credits
This article is adapted from the Wikipedia article “True length”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Axonometric projection.svg by Yuri Raysper, Public domain
- Dodecahedron flat.svg by Júlio Reis, CC BY-SA 3.0
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