In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures is constructed to represent the form of a three-dimensional object. Up to six pictures of an object are produced (called primary views), with each projection plane parallel to one of the coordinate axes of the object.
The views are positioned relative to each other according to either of two schemes: first-angle or third-angle projection. In each, the appearances of views may be thought of as being projected onto planes that form a six-sided box around the object. Although six different sides can be drawn, usually three views of a drawing give enough information to make a three-dimensional object. These views are known as front view, top view and end view. Other names for these views include plan, elevation and section.
To render each such picture, a ray of sight (also called a projection line, projection ray or line of sight) towards the object is chosen, which determines on the object various points of interest (for instance, the points that are visible when looking at the object along the ray of sight); those points of interest are mapped by an orthographic projection to points on some geometric
even if the faces of the box are unfolded in one standardized way, there is ambiguity as to which projection is being displayed by a particular face; the cube has two faces that are perpendicular to a ray of sight, and the points of interest may be projected onto either one of them, a choice which has resulted in two predominant standards of projection: