Ombre e riflessi nella rappresentazione tecnica e artistica

The theory of the shadows has remained marginal for a long period in most of manuals of descriptive geometry and digital methods now allow the determination of cast shadows through the display of virtual models to a variety of light conditions and environments. The treatment of the traditional graphical procedures seems, therefore, unnecessary, but, in contrast, is justified as background for a conscious management of the shadows of three-dimensional model, which allows the designer to govern the logic of the software adopted, and not remain at the mercy of the limitations that, as we know, all the instruments have. For this reason, we describe an original unified procedure for the detection of shadows in different methods of representation of space on the plane, in a context of traditional descriptive geometry. The system exploits the peculiar characteristics of individual methods for the detection of accelerated procedures, through the recognition of shadows as objects to represent themselves. Once generated from the system which consists in the object that casts the shadow, the light source and the surfaces on which they project, shadows can be treated, in fact, as independent objects, which are added to the original subject to be represented. It is created the definition of "graffiti" system to indicate the procedure aimed at identifying the contours of shadows, using the projective properties shared by different methods. Furthermore, modern digital modeling tools allow us to recover the complexity of the physical phenomenon of light, in descriptive geometry often limited only to represent shadows cast upon themselves and upon other objects. We can also describe more complex phenomena of light, reproducing the intensity of illumination, or the effects of diffuse light, reflection and refraction. Rendering effects allow a detailed study of the response of various materials to their exposure to light, allowing you to easily determine the images reflected on any kind of geometric surface. It is from the analogy of the projective fundamentals of the formation of shadows and reflections that comes the interest of revisiting some paintings of the masters of Renaissance and Baroque. We can use digital methods and even try to compare the works of art with contemporary theoretical knowledge. Traditional methods are, therefore, an invaluable tool for managing the design sketch or control of the digital modeling, but also help to preserve an interpretation for the drawings of the past, heritage of the history of representation.