Interpreting Bastion Geometry: Digital Methods for Investigating Dutch Early Modern Military Architecture Through Freitag’s Design Principles

Abstract This paper presents a computational framework for the automated geometric analysis of bastion fortifications, tested against the Freitag design principles, developed in the Grasshopper Add-on of Rhinoceros 3D. The system identifies key elements—curtain walls, bastion flanks and faces, shoulders, and salient angles—within regular polygonal layouts. It calculates five defining angles per bastion and proportions such as the gorge-to-interior base ratio, enabling comparison with design norms from 17th-century Dutch military treatises. Tested on 13 early modern bastion castles, with four detailed case studies (two pentagonal and two square-based), the framework extracts consistent morphometric data from CAD plans. Unlike prior research that parametrizes treatise rules to generate ideal fortification forms, this study reverses the process, applying analysis to real layouts to assess their conformity to Dutch standards. The approach combines computational geometry with historical interpretation, providing a scalable and reproducible method for typological evaluation.