The main objective of the course is to show and experiment with the complex production process of product design from the point of view of design and representation. Starting from the sketch of the project, the idea is refined through increasingly detailed drawings, up to the technical executive representation. This defines the main communication tool of the project between the designer and his producer, so it requires a formal and regulatory correctness. But this structured drawing also represents the starting point for the construction of 3D models with increasing geometric complexity, up to the definition of reality-based 3D models, from which realistic or functional images and 3D prints can be extracted. Inversely to this process, always structured within the design workflow, there is the process of reverse modeling, understood as the translation of an existing product in its digital copy, starting for the design intervention on the existing. The drawing becomes the means of creation of the design product, while the representation assumes the dual role of prefiguration of the idea and virtual window of reality. During the course students will learn how to manage the models listed above, acquiring the ability to control the dual path of design, from real to virtual and back. In this context, the differences between the representations for the project and for the survey, the scales of representation and the levels of accuracy in the representation and modeling will be investigated. Some exercises on design themes will allow to understand the relationship between the generators, the directions, the style lines and the structuring geometries within the digital models.