Optical illusion is a playground for artists.  Every artist who depicts a solid, “real” object on a 2-dimensional canvas strives to create the illusion that the object viewed is 3-dimensional; the artist can employ a host of visual tricks to accomplish that goal.  For centuries, masters of trompe l’oeil (fool the eye) have created illusory cornices, windows, balconies, and doors to enhance or enliven otherwise bare walls.

In 3-dimensional space, artistic tricks are not needed to produce illusory images.  Instead, our eyes and brains themselves supply us with illusions: we see, or think we see, something that is not really what it is.  If you look straight into a shallow round bowl, for example, your brain might not be able to determine if the shape is concave (scooped out) or convex, like a mushroom’s dome. 

The viewpoint from which we observe a 3-dimensional object can be crucial to our “seeing” and understanding the object.  Unless the object is transparent, we cannot see parts of it that are obscured by other parts covering them.  We can only see a projection, or shadow, of what is directly in front of us.  Bakker capitalizes on this property so that his sculptures provide teasing optical puzzles: if I observe the sculpture from this viewpoint, can I guess the full sculpture’s shape?  Only by rotating the sculpture in space, viewing it from many angles, can you discover its surprising symmetries.