The history of Palladian digital 3D models from the spatial grammar to the semantic construction

In this paper we present a critical history of the Palladian digital 3D models starting from the Stiny & Mitchell spatial grammar to the reconstruction as ‘instauratio’ suggested by one of the authors during the years 1990, finally to the semantic modeling developed from the end of the last century. This narration is in our opinion central in the whole history of the digital 3D reconstruction applied to the architecture field, mainly for the strategy followed. Palladian 3D models construction techniques and the final outcomes, marginally follow the well-recognized path of photorealistic interpretation of a lost past, a re-interpretation of the photorealistic appearance of the envois of the French architects pensionnaires in Rome during the XIX century. In the Palladian case the use of digital technology as interpretation tool involved a philological analysis of unbuilt projects, unfinished works and disappeared architectures developing - as shows the rich and systematic contributions of William Mitchell - techniques and methods to construct the 3D models as cognitive and interpretive system. The feature of Palladio’s drawings to be flattened patterns of spatial solutions and the existence of a grammar described by the architect (its The Four Books of the Architecture), allowed many attempts to reconstruct the complete project from partial representations, with the aim of discover design intents, the logic of architecture and possible interpretations of the original drawings. Our paper aim to describe not only the many attempt and results from different group, but also to provide an in-depth analysis of methods and techniques, both investigating its origins in architectural design and methods of historical architecture analysis, and illustrating digital implementations and developments allowed significant contributions to capture the qualities of the built projects, the deficiencies of those abandoned, the complexities that have endangered some achievements.