The general rule seemed to be "no underwear"...
Or, if you were wearing underwear - for example, pants - you were required to have them on display via a transparent skirt...
For those of you now wondering why Delta Goodrem made the header image despite her not having her underwear on display - it's because she chose to wear a transparent skirt - with pants AND opaque tights. Novel.
... that and she was also one of the few recognisable people there - apart from Charli XCX and The Veronicas.
Taking the 'leave nothing to the imagination' memo to new levels was this interesting couple which WENN have unfortunately seen fit to remain nameless.
Finally, one of the biggest names there opted to remain fully clothed (to the point of overcoats despite it being summer in Sydney right now). Niall, put those arms away - you'll be burned to a cinder!