The shape of an upcoming new car is always a well-kept secret, but the need for prototypes to test on public roads has traditionally provided the automotive press with plenty of opportunities for spying.
Hunting down camouflaged test cars has become such a ritual that occasionally carmakers now openly show them off.
Taking an opportunity for some advance publicity while still keeping the final design under wraps, General Motors has done exactly that with the 2016 Chevrolet Volt extended-range electric car.
And it offered some information on how the camouflage designs are created, while saying nothing at all about the actual car under the camo.
2016 Chevrolet Volt - first teaser image, Aug 2014
Camouflage designers have to balance the priorities of the design team--which wants to hide the car's true appearance as much as possible from the public--with engineers who want the test vehicle's weight and aerodynamic profile to be as close to production-spec as possible.
This is particularly relevant to the Volt, which relies on a slippery shape for maximum efficiency. Protrusions that might fool spy photographers could significantly affect the car's performance.
Carmakers also rely on graphics--such as the swirls seen in the photo above--to break up a car's outline and hide details, similar to the "dazzle" camouflage applied to ships during World War II.
Three-dimensional layering can also achieve this effect.
Camouflage can be made of different materials such as plastic, vinyl, or foam, but bubble wrap works particularly well, according to GM.
2015 Chevrolet Volt
So that's the story of the camouflage, but what about the car underneath?
The 2016 Volt is expected to have an evolved version of the current model's styling, and retain the same five-door hatchback layout.
GM's tease image hints at that. The car has a steeply-raked windshield and high hood line, just like the current Volt.
Scheduled to debut at the 2015 Detroit Auto Show in January, the 2016 Volt could also feature more radical changes under the skin, including a smaller, 75-horsepower gasoline range extender.