Once an idea starts to take shape from rough sketches or models, 3D CAD is used to create accurate geometry of and around internal components. Using 3D CAD is critical in being able to design from all viewing angles. It also helps in communicating design concepts clearly with fully rendered images, sections and exploded views. Typically the design takes on an evolutionary process with multiple iterations. At some point, physical models are needed to get a sense for the product size and for testing functionality.
This realistic rendering, of a pair of sandals for DC Shoes, was generated with 3D CAD to provide a clear view of what was about to be 3D printed and manufactured.
Other 3D examples
PlaneDriven Wheel Pants
Design exploration for a stand up catamaran.