A method and device for determining a footprint of a 3D structure are disclosed. The method includes: receiving mesh data for the 3D structure that includes vertices and edges that form polygons of the 3D structure; determining a connection graph including candidate nodes and candidate lines by (i) identifying all edges having a vertex that is less than threshold height value, and (ii) mapping the identified edges and vertices thereof onto a 2D plane; determining an adjacency list that indicates, for each candidate node, which other candidate nodes are connected to the candidate node by a candidate line; and generating a footprint of the 3D structure based on the connection graph and the adjacency list, the footprint including vertices corresponding to a selection of the candidate nodes and including edges corresponding to a selection of the candidate lines.