I haven't looked at that side of things - but, one thing I have noticed is that some women, who, technically, have very good bodies -- and, are sexy much of the time - something goes terribly wrong when they take their clothes off
Amanda Peet is one of my better examples -- and a good eg. is in 'The whole nine yards' - where she is full of life and energy and looks sexy much of the time with her clothes on - but, when she gets naked (leaning out the window scene) - well, there's just nothing there.
Possibly it's something in her character in the movie - because in either 'The whole nine yards' or 'The whole ten yards' she plays a seductive part - and, is about the most unsexy thing I have seen in a long time - it is a spoof movie though and the scene is meant to be comical - -but, there is no getting away from it - that in the scene - she just wouldn't convince anyone to get aroused. Although she is 'acting' an 'acting' part - one would have expected some sort of sexual interest - but, nope, zilch.
I have also observed a not dissimilar thing with Amy Adams sometimes -- who can be very hot in clothes, but, not hot at all if she isn't dressed well, even if she is showing a lot of flesh.
On another hand, you have Julia Roberts, who, if you break her body structure, stance, walk etc. down - it's not really good - but, when she wants to she can turn a light on from a kilometre away - clothed or not.
The whole area is a very complex mix of body language, attitude, chemistry etc. with physical looks coming a long way back in the field IMO.
Probably the most fascinating area is the difference between stage and screen - where often, a phenomenal stage actor or actress who can just light up a theatre -- falls completely flat on screen.
There's a magic energy that some have in life that just refuses point blank to go through a camera lense.
