Abstract: In example embodiments, techniques are provided for enabling use of an AI-generated TIN in generation of a 3D design model by defining site objects (e.g., pads) using multiple (e.g., three) phases (i.e. states). A conceptual phase may be associated with a conceptual data structure, a preliminary phase may be associated with the conceptual data structure and a preliminary data structure, a final phase may be associated with the conceptual data structure, the preliminary data structure, and a final data structure. If changes are made in the conceptual phase, for example, as a result of AI optimization, they may be propagated up to the preliminary data structure and final data structure via the vertical draping. Changes made in the preliminary phase or final phase may be propagated down to the conceptual data structure by treating boundaries and breaklines as spatial constraints.