Optical illusion: The Penrose triangle

The Penrose triangle, also known in French language as the “tripoutre” or “tribarre”, is an impossible object designed by the mathematician Roger Penrose in the 1950s. In fact, this object can only exist on two dimensions, drawn on a piece of paper, and never in the physical reality.
This is an important figure in the work of the artist Maurits Cornelis Escher.
This figure was first described in 1934 by Oscar Reutersvärd (1915-2000), and Penrose designed it in 1950.
It was rediscovered by Penrose who publishes the drawing in the British Journal of Psychology in 1958.
The “tripoutre” can only exist in the form of a two-dimensional drawing, because it uses overlapping parallel lines drawn from different perspectives. It represents a solid object, made of three square beams. All the beams are perpendicular to the other two and form a triangle.
However, it is possible to create a solid object resembling Penrose triangle: such forms can be either curved or have a break, but viewed from a certain angle they give the illusion of complete triangle.