Optics principles. For example, the Ames room, Hering, Müller-Lyer, Orbison, Ponzo, Sander, and Wundt illusions all rely on the suggestion of the appearance of distance by using converging and diverging lines, in the same way that parallel light rays (or indeed any set of parallel lines) appear to converge at a vanishing point at infinity in two-dimensionally rendered images with artistic perspective. This suggestion is also responsible for the famous moon illusion where the moon, despite having essentially the same angular size, appears much larger near the horizon than it does at zenith. This illusion so confounded Ptolemy that he incorrectly
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