Piero della Francesca’s contribution on the apparent contour perspective

The discerning of the visible part of an object from its invisible part, with respect to the centre of projection, is one of the problems that must be addressed in the representation of any object. The dividing line between these two parts is what we now call the apparent contour. In the history of representation, the study of this theme must be found in the analogies with the condition of illumination of bodies: when the light source is at a finite distance, this can be compared with a proper projection centre, as is the case of perspective. The research for the apparent contour is an easily solved problem in the case of a multifaceted object, otherwise, in curved or free surfaces its identification is more complex. The present study intends to investigate the important contribution provided by Piero della Francesca's work in De Prospectiva Pingendi to scientific theorizing on the central projection of the apparent contour. In this treatise, Piero addresses the theme in three cases: in the anamorphosis of the sphere and the goblet and in the perspective of the human head.