The artist Oscar Reutersvärd was probably the first to make so called impossible figures, starting in the 1930s. The triangle made of cubes shown to the right is one of his creations. Roger Penrose and Maurits Escher have also made well-known figures of this kind.
The seeming impossibility of these figures derives from the fact that each part of them can be interpreted as a projection of a three-dimensional object, but the entire figure cannot. Some of the figures add another element to the visual illusion – figure and background seem to be mixed. An example is the so called Devil’s fork (right).
This feature is what I focus on in my own pictures, forgetting about three-dimensionality and perspective. Each line seems to be a contour of an object. We tend to interpret one side of the line to belong to the object and the other side to belong to the background. However, this interpretation only makes sense in each small part of the picture, not in the picture as a whole, just as the perspective in traditional impossible figures only makes sense in each small part of the figure, not in the figure as a whole.