We develop a new kind of "space-filling" curves,  connected Fermat spirals , and show their compelling properties as a tool path fill pattern for layered fabrication. Unlike classical space-filling curves such as the Peano or Hilbert curves, which constantly wind and bind to preserve locality, connected Fermat spirals are formed mostly by  long, low-curvature  paths. This geometric property, along with continuity, influences the quality and efficiency of layered fabrication. Given a connected 2D region, we first decompose it into a set of sub-regions, each of which can be filled with a single continuous Fermat spiral. We show that it is always possible to start and end a Fermat spiral fill at approximately the same location on the outer boundary of the filled region. This special property allows the Fermat spiral fills to be joined systematically along a graph traversal of the decomposed sub-regions. The result is a globally continuous curve. We demonstrate that printing 2D layers following tool paths as connected Fermat spirals leads to efficient and quality fabrication, compared to conventional fill patterns.
['Haisen Zhao', 'Fanglin Gu', 'Qi-Xing Huang', 'Jorge Garcia', 'Yong Chen', 'Changhe Tu', 'Bedrich Benes', 'Hao Zhang', 'Daniel Cohen-Or', 'Baoquan Chen']
Connected fermat spirals for layered fabrication