>>1895625It's in-engine using belts; the back part of the dress behind her legs is just a copy of the girl in the same pose with a belt positioned there. In order for her cleavage to look like there's something holding it in place as she's not wearing an actual top as far as the engine is concerned you have to put underwear on her and then make it invisible by holding down the 9 key. This will position the girl's breasts as they would be under clothes so they look like they fit into the dress.
Due to the way belts clip at the edge of the body and overlay arms you are really limited in poses doing that though.
Here's another using belts to make clothes parts, it's all stuff you can do in the program itself with no shooping necessary.
