The Nonplanar Slicing was started in 2018 with a Master thesis. The general idea is to remove the stair-stepping effect on surfaces that are close to horizontal by printing these areas with nonplanar layers. With this approach, the printable areas are detected automatically and checked for possible collisions while printing. The area below the nonplanar surfaces is printed with a regular planar structure. The modified Slic3r then generates a nonplanar toolpath on top off the regular layers. This technique leads to much smoother surfaces due to the missing stair-stepping effect.

All implementations are done in Slic3r and available under a GPLv3 licence on Github: https://github.com/Zip-o-mat/Slic3r/tree/nonplanar.