Provided are a system, method and computer program product for generating three dimensional models for use by an additive manufacturing or 3D printing system, in which object model data defining one or more objects to be built by a three-dimensional printing apparatus is input and used to generate a three dimensional model for a protective structure to surround the one or more objects. A user is provided with selectable configuration options for the protective structure. The method includes presenting, via a user interface, selectable configuration options for a protective structure to be built around the one or more objects by the three-dimensional printing apparatus. In response to user selection of one or more configuration options via the user interface, a three dimensional model for the protective structure is automatically generated.