  This work presents a halftoning technique to manufacture 3D objects with the
appearance of continuous grayscale imagery for Fused Deposition Modeling (FDM)
printers. While droplet-based dithering is a common halftoning technique, this
is not applicable to FDM printing, since FDM builds up objects by extruding
material in semi-continuous paths. The line-based halftoning principle called
'hatching' is applied to the line patterns naturally occuring in FDM prints,
which are built up in a layer-by-layer fashion. The proposed halftoning
technique isn't limited by the challenges existing techniques face; existing
FDM coloring techniques greatly influence the surface geometry and deteriorate
with surface slopes deviating from vertical or greatly influence the basic
parameters of the printing process and thereby the structural properties of the
resulting product. Furthermore, the proposed technique has little effect on
printing time. Experiments on a dual-nozzle FDM printer show promising results.
Future work is required to calibrate the perceived tone.
