preliminary drawing or sketch
A drawing (sketch) or a plastic model, made to study, design or give an idea of the appearance of an object, or of its functioning.
By sketch we mean the graphic version, the preliminary design of a work.
It was born for the author's need and also for the purpose of illustrating the general characteristics of the creation, of making the idea easily understandable and of studying possible developments to be transferred to the finished product.
The sketch or draft assumes different names and meanings, as well as manufacturing techniques, depending on the type of work that is "sketches".
Often the sketch, the subsequent processing and evolution, are an integral part of the project and determine its main characteristics, then developed and refined in the final design and construction of the executives.
The sketch is used in many fields of art and design.
In sculpture, the sketch is often used as a scale model of the final and is used to create and study the composition.
If a particular quality has value in itself, as a graphic work, demonstrating and communicating effectively with the spirit which moved the creative act and design.