Trompe-l'œil & Forced Perspective

Trompe-l'œil (French for deceive the eye) is an art technique that uses realistic imagery to create the optical illusion that the depicted objects exist in three dimensions. Forced perspective is a comparable illusion in architecture. from Wiki

https://www.altaplana.be/dossiers/darius/the_walls_of_samaris_part_2_the_trompe-d_oeil_and_you


Some of the Forced Perspective Illusion

> Stage Set - Teatro Olimpico

Trompe-l'œil, in the form of "forced perspective," has long been used in
stage-theater set design, so as to create the illusion of a much deeper
space than the actual stage. A famous early example is the
Teatro Olimpico in Vicenza, with Vincenzo Scamozzi's seven
forced-perspective "streets" (1585), which appear to recede into the distance.

Illusion of scene transition

The Illusion of Scene Transition make use of perspective theory in large scale visual "realities" together with the actors/ actresses on stage, created an immersive experience to the observer in the audience seat. The mathematic calculation of perspective on the triangle surface allow quick transition during the play. 

> Film Making - Create a HOBBIT-sized Illusion

Forced Perspective technique 

http://photography.tutsplus.com/tutorials/how-to-create-a-hobbit-sized-illusion--photo-17610

In order to create illusion of dwarf and giant tall wizard with normal human, the actors are arranged in different distance with the camera. According to the theory of perspective, the same items will looks bigger when it's nearer to the observer, and it appeared to be smaller when it's placed in further distance to the observer. In set design, props that used by the giant will needs to be smaller than the usual size we have. For example the cup on the wizard hand above, is a smaller version of the normal cup to create illusion of a giant. While the dwarf character above, (seating further away from the camera) has a plate the is larger than usual plate size so that when it's place at the further distance, it'll still looks like it's at the same distance with the wizard.  

> Wall Paint - Trompe L'Oeil PRACTICAL.

Conclusion

With the collection of techniques used in variety art forms like Stage Performance, Interior Architecture, Filming and Painting, the idea of illusion share some of the similar points.

When observer maintain a distance with the artifact, the use of perspective techniques, lights and shadow position, camera angle will affect the physiological aspects of optical perception.