Today no one is surprised by the ability to recreate gradient banners and photographical images, transitioning into a blank sheet or into another image, with the help of CMKY printers. Also, sound can be smoothly increased and light can be gently dimmed. Taste can change from sweet to bitter, smell can change from pleasant to irritating. All the above processes are manageable. So, if a 3D object can be printed like a 2D one, you could assume the appearance of pieces with mixed characteristics of materials.
To begin with, the printer should be able to print an object with changing transparency.
Secondly, which is the most unbelievable but logical, the printer should print an object with mixed physical characteristics. Today a large number of materials for 3D printing already exist. We can achieve objects that greatly resemble original materials, ceramics, rubber, metal, glass etc.
Therefore, similarly to 2D printing, an opportunity to produce objects with blending physical characteristics will appear, for example, changing from a metal foundation to a transparent glass plafond or from a plastic handle to a metal knife, or from a wooden handle, to metal dipper of a spoon.
But even this is not everything that can be expected. I dare to suppose that at a time when there are designs managed by CMYK characteristics of markers and cartridges, which will most definitely appear in the foreseeable future, objects possessing manageable physical characteristics will develop.
For example, you will be able to choose the material for the handle of a knife, the wooden can be changed into plastic, plastic into rubber, and it will also be possible to do that with the blade. You would be able to twist a rubber knife and hide it in your pocket.
3D printing is only beginning its journey; this is a revolution not only in the creation of the objective world. Technology allows performing actions that seem absolutely fictional, for example, printing a ripe pear or anchovy with pickles, in addition, serving a glass of white wine with a taste of the rarest natural sort.