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
The Colossus (painting) crowd. The effect of the light, which possibly indicates sunset, surrounds and highlights the clouds that encircle the giant's waist as described in Arriaza's poem: This slanting light is fractured and interrupted by the mountain peaks increasing the sensation of disequilibrium and disorder. The effect is similar to Luis de Góngora's famous "dubious daylight" ("Fable of Polyphemus and Galatea" v. 72.). Instead of a centripetal composition where all the indications point towards a central nucleus, in this painting all the lines of movement shatter the unity of the image into multiple paths towards its margins. The painting can be considered