Concept Exploration Using an Underlay - Gatorade Packaging

What is an underlay? Why do designers use them? How can I use an underlay to develop solid solutions for my client? Christopher Lavelanet, an independent contract designer who travels between the US and the EU, has utilized underlays to easy overcome the spacial and volumetric hurdles designers sometimes face when developing design solutions. An underlay is a reference image used by designers to eliminate the need to redefine overall proportion each time they begin to develop a new concept. In the example shown above, the underlay is a simple line drawing, probably taken from a 3D cad drawing, the defines the volumetric considerations the designer needs to stay within as he develops his solutions. He then places another piece of paper, perhaps vellum, tracing paper, graphics 360, etc. on top of the line drawing and uses it as a reference for his design explorations. Underlays also serve to eliminate the need for the designer to redefine the perspective, scale, and proportions that are more easily tackled by using an underlay. This is only a tool used by designers to speed up their process.Once the sketches and simple shading are completed the designer can then take the newly defined concept and add some color so that they are more easily read by those that aren't as visually enabled as the designer.