The photo below was an experiment in optical illusion. We were looking to see if we could print a 3D model that would actually look like a classic CAD image - complete with the geometrical design lines.
Did we succeed? I think so. Most people looking at the image below assumed that we'd superimposed a CAD of an avocado onto the photo of the bowl of fruit. They didn't realize it was actually a real 3D printed model sitting in there with the rest of the fruit.
This effect was only possible using the Objet Connex multi-material 3D printer which can simultaneously print the 'solid' shape of the avocado (in Objet VeroClear transparent material, pre-polish) and the embedded design lines in Objet VeroWhitePlus.
(Above) Superimposed CAD Image or Real 3D Printed Model?
(Above) Close-Up of the Avocado with Detail of Geometrical Design Lines