Il capitello ionico classico e gli esiti inaspettati di un suo modello numerico

Current trends reveal a revival of studies on the design of orders. These studies provides us with greater knowledge of the forms and shapes of classical architecture, its proportions and its aesthetic parameters. This renewed interest inevitably means that advanced technologies are now used to study classical orders. Computers can draw orders in space and verify their true configuration. The method chosen here compares Vitruvius’ description of the orders and their components with the interpretation elaborated during the Renaissance and recorded in treatises. For this reason, all the drawings of these scholars, considered as experimental or design theories, were re-elaborated using a CAD program. The same partition method used in the treatises was then applied. It is interesting to note how this centuries-old operational logic is similar to the CAD, since it too is based on algorithms. As far as the Ionic capital is concerned, the interpretation of the scholars contains no important differences. Similarly, they all agree with Vitruvius on the projection of the echinus. However they differ in regard to the tracing of the volutes. As long as the CAD is used only to verify the tracing and proportions of a flat drawing, the contribution that computers can provide in the study of Ionic capitals is limited. Instead when the CAD is used on a three-dimensional plane to construct a model capital, it highlights a glaring anomaly that has gone unnoticed in three centuries of research. If the echinus is built according to the accepted interpretation of Vitruvius’ writings, its volume intersects the volutes more or less at the “piumette”: Not only is this unacceptable but furthermore, it has never been recorded in any historical document. Vitruvius’ description can be interpreted in many ways. In fact, in historical documents of the ancient world, the echinus often projects less than Vitruvius would have wished. The problems surrounding the configuration of the echinus are threefold. They relate to the projection of the echinus, to the curvature of its surface and to the consistency of the vertical section of the echinus itself. The survey, carried out with the help of templates, made a detailed study of three classical Roman capitals in the Museo Nazionale Romano near the Diocletian Baths. The templates were used to measure the vertical sections of the echinus radially, from the centre outwards, as well as different levels of the horizontal sections. Traditional survey methods were also used to take the more important measurements of the capital that were necessary to elaborate the basic design module. Once the sections were scanned they were transferred to the CAD to be re-elaborated. These elements already show a number of differences with respect to the theoretical state of the echinus. However, the method chosen was to place them in space in the same position in which they were surveyed and then build the three-dimensional model of the surface in question. The comparison between the models elaborated by the survey and the models drawn up considering the surface of the echinus as a typical rotational surface does provide clear results. All of the capitals, to one degree or another, were affected by the corrections mentioned earlier.