>>14612637A little of both. It's not quite the push-up bra analogy, since her butt is completely exposed. That mass is actually there, it doesn't come from no where, but the straps do sink her thighs and create an artificial fold for the cheeks to poke out more. They don't create more mass, just enhance the shape.
A push-up bra is a little different, in that it actually displaces mass, but then also covers up the area the mass was displaced from, giving the illusion of more overall mass.
But yes, functionally they are pretty much the same, as in "article of clothing which enhances the appearance of the female form".
