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
Skew lines value of the real number formula_4 determining where the point is on the line, and similarly for arbitrary point on the line through particular point in direction . The cross product of b and d is perpendicular to the lines, as is the unit vector The distance between the lines is then (if |b × d| is zero the lines are parallel and this method cannot be used). Expressing the two lines as vectors: Line 1: formula_7 Line 2: formula_8 The cross product of formula_9 and formula_10 is perpendicular to the lines. formula_11 The plane formed by the translations of