G-code slicing. Slic3r vs Cura. G-code slicing Once a 3D model has been created there is an essential step before being able to print the object. The 3D model must be sliced into layers and the output translated to a numeric control language called G-code. Slicing software exists and is very user friendly. Two of the most popular (as well as free) versions of this type of software are: Slic3r and Cura. Slic3r Slic3r .