===== Extrusions =====

Extruding a two dimensional shape into a three dimensional shape can be performed in various ways. In each extrusion process, a continuous three dimensional shape is formed with a constant cross section similar to that of the two dimensional shape.

//NOTE: In order for extrusions to produce correct shapes, the initial two dimensional shape must have the proper orientation. See [[en:math_guide_orientation|Orientation]] below.//

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===== Projections =====

The projection of a shape is a two dimensional representation of a three dimensional object. In this case, the projection is a parallel projection where the lines of projection are parallel, i.e. the projection is the same whether the shape is far away or near to the projection plane.

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