I always thought 4D was time, but according to the fashionable people at Ralph Lauren, 4D is actually perfume wafting out of huge projected-upon stores. Even if you're dressed in hoodie and jeans, you'll still find this quite impressive.
It was all in aid of Ralph Lauren's 10th anniversary of their online shop, with shoppers on Madison Avenue in New York and New Bond Street in London being treated to a visual show for 10 minutes, where the buildings were projected on in a pretty astonishing way.
Looking like they were distorting and bending, the buildings were lit up and down, and even had galloping horses and mammoth catwalk models shone on them. It wasn't 3D projection, sadly (I imagine 3D glasses aren't yet fashionable enough for the fashion crowd - however much Gucci may try), but Ralph Lauren was claiming it was a "4D show" thanks to the wafting perfume, music, fake breezes and other non-tangible effects. [LDN Fashion]
The video of how this visual-mapping extravaganza was created is quite an interesting watch: