Graphical projection Perspective projection is a linear projection where three dimensional objects are projected on a "picture plane". This has the effect that distant objects appear smaller than nearer objects. It also means that lines which are parallel in nature (that is, meet at the point at infinity) appear to intersect in the projected image, for example if railways are pictured with perspective projection, they appear to converge towards a single point, called vanishing point. Photographic lenses and the human eye work in the same way, therefore perspective projection looks most realistic. Perspective projection is usually categorized into "one-point", "two-point" and "three-point
Distance from a point to a line length of this projection is given by: Now, thus Since "Q" is a point on the line, formula_27, and so, It is possible to produce another expression to find the shortest distance of a point to a line. This derivation also requires that the line is not vertical or horizontal. The point P is given with coordinates (formula_29). The equation of a line is given by formula_30. The equation of the normal of that line which passes through the point P is given formula_31. The point at which these two lines intersect is the closest point on the original line