Although we’ve come across some beautifully detailed, creative, and seemingly realistic 3D printed objects in the past, such as this life-like prosthetic hand, or these artificial organs used for surgeon training, one of the biggest challenges facing 3D printing is the ability to print in full, highly detailed, true-to-life color.

The objects mentioned above are nearly perfect in terms of their shapes and applications, but aesthetically, there has always been somewhat of a lack.

A recent publication, however, is about to change all of that. A team of researchers at the Fraunhofer Institute for Computer Graphics Research in Germany has created a new technique for producing accurate colors in 3D printing for the first time. Don't beleive us? Just look at the picture below. Only one of those apples is 3D printed, but you'd never know which.

The reason full color 3D printing has remained a challenge for so long is because in traditional FDM or SLS 3D printing, objects are created by fusing either powder or plastic layer by individual layer. Further, since most printers only a single head extruder, they can only print in one material, or one color, at a time. While it is possible to stop a print mid-job and switch the filament for a new color, or to use multi-colored strings of filament, the results are often pretty rudimentary. Airbrushing or painting objects by hand has also an option, for only for the artists among us.

The beauty of the new color printing process, developed by Alan Brunton, Can Ates Arikan and Philipp Urban, however, is that the objects are imbued with incredibly detailed and precise colors during the printing process. Known as an ‘error diffusing halftone’ approach, the technique actually utilizes some of the principles used in 2D color printing, such as building up an image pixel by pixel, and relies on multi-jet 3D printers such as the Object500 Connex3. So, rather than laying down prints layer by layer, objects are built up and color-treated voxel by voxel. The result is an incredible amount of control over each and every ‘droplet’ of ink, and the most realistic colors possible to date.

In developing the process, Brunton and his team faced some pretty serious challenges. The first is the sheer amount of data needed to design and keep track of all those voxels—a single cubic centimeter contains up to 18 million of them, so even a palm-sized object would be made up of billions. For the color technique to work best, the color and shade of voxel needs to be carefully taken into consideration. The second challenge is that the ‘droplets’ that make up multi-jet printed objects must be instantly cured by UV light in order to solidify, however this also means that they must be somewhat translucent in order for the light to pass through them. This means that the color of each voxel will impact the ones around it.

In order to solve this ‘transparency problem’, the researchers have proposed a “novel traversal algorithm for voxel surfaces, which allows the transfer of existing error diffusion algorithms from 3D printing”—a very scientific way of describing an algorithm that can predict how light will diffuse through the translucent, 3D printed object, and color each voxel accordingly to achieve the perfect shading from the inner to outer layers.

The results are already truly stunning, and even a little uncanny, particularly the realism of the man's face pictured above. The applications for this kind of technology could have a huge impact on how people think of 3D printing and even bring it further into mainstream acceptance—just imagine 3D printed prosthetics that truly imitate the surface of human skin making them almost undetectable.

And if that wasn’t good news on its own, Brunton and his team are already confident that the technology will only get better in the very near future as less translucent 3D printing materials are developed and as even higher resolution printers are released. Life is meant to be lived in full color, and thanks to this new development, 3D printing will be too.

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