Sammy Feld

Looking the big complex huds of product like the ones provided with mesh body or mesh heads I cannot figure out how they could work. I mean, there's a lot of clickable areas, with very complex shape (not just a square or a circle) and very close each other (without gap between each other). As noob scripter I cannot figure out how they can function, there's no invisible clickable prim, they don't (I think) compare mouse coords with a matrix of point to detect what you are clicking, as far I see they don't pickup color from pic or do anything else I can imagine.. Anyone know how they get that result? ..if it's a too complex explanation to write down could you provide me a link, or an info source I can read / study to find the answer? Thank you (in advance) !

At my eyes is: https://marketplace.secondlife.com/p/BURLEYBabsIISampler-wear/7332553 the red nuance. Same shop hase the relative demo to "try before you buy" : P