Architettura ovata e tracciamento geometrico/Ovate architecture and geometric tracing

From visual-perceptive point of view, an ovate shape is characterized by a curvilinear elongated profile provided with double orthogonal symmetry. Sebastiano Serlio in his Architecture Treatise ‘First Book’ (Paris 1545) describes how this profile can be traced in three ways: ‘with thread’, ‘with the compass’, ‘guided by reason’, that correspond to three different shape geometric definitions: ellipse, polycentric curve, circle’s homological transformed. Taking a cue from the ovate shape experimentation in civil, religious and military architecture, we will examine the treatises and manuals sources about the ovate shape geometric tracing applying the so-called ‘with thread’. The analysis will be carried out through the following steps: analysis of the old mathematical sources; encoding the rule theory (Serlio, Cataneo, Lorini, Accolti); geometric tracing ‘on the ground’ with ‘the gardener rule’ (Bosse, Blondel, Dézallier d’Argenvielle); geometric tracing ‘on the paper’ through the use of a continuous line mechanical instruments (del Monte, Bosse, Blondel); analysis of developments and applications in the eighteenth and nineteenth centuries (Guarini, Bélidor, Encyclopédie, Rondolet, Breymann, Curioni and Donghi); graphical analysis for the Serlio’s “Oval Temple” project.