Designing for outdoor applications comes with a plethora of challenges and hurdles, from materials and substrates to legibility and visibility. The biggest factor is the environment itself - what forces outside of your control will change what people see?
Sometimes, however, a rare idea strikes us that not only accounts for an environmental factor - it actually relies on it. Check out the image above of BBC One's "Dracula" billboard, which seems relatively stark during the day, but at night the attached spotlight allows the dimensional stakes to create an ominous shadow of the titular vampire.
It reminds me of an anti-domestic violence campaign from last year, where the billboards had a lenticular effect that when viewed from an average adult height looked like a completely normal person, but when viewed by someone under 4-5ft tall (such as a child) showed obvious signs of abuse and offered information on how to report that which often goes unseen.
It's difficult to come up with how to utilize the environment in which a piece will be viewed to our advantage. So many of those factors are outside of our control - there is no way to guarantee that a shadow will fall in a particular fashion without having control over the lighting, so the lighting becomes a part of the installation. While not all of the effects can be translated into a 2-dimensional space, there are certainly some unique ideas that can come when we challenge ourselves to think about our designs in terms of depth and dimensions.