The metric illusion is also known as an ambiguous figure or as an inside/outside illusion. This kind of visual optical illusion is representative for the multistable perception. The illusion is created basically through any shape of the same-length lines that don’t indicate in a clear way their direction. Today’s illusion was created by Sol LeWitt and it can be seen at the National Gallery of Art Sculpture Garden in Washington.
What to see?
This illusion consists of blocks arranged in a precisely manner to form a pyramid. When there is a bright light and you look at the pyramid the shadows and the extremely white blocks play tricks on your mind.
The contrast creates a so called flip-flopping optical illusion, where it isn’t clear what way the blocks are oriented.
How it works?
The Four-Sided Pyramid represents a 3D structure and it uses projections in which the angles of the drawing or structure are not equal, even if mentally we know they are.
This illusion can take place due the incidence of light. There are some illusions that appear at first to be normal and simple perspective renderings of solid, 3D objects or scenes, but if you try to analyze them you will notice some internal contradictions: the 3D object or scene can’t exist in the real life.