They can be surprisingly useful, but not in the way you would intuitively expect. Herewith is another technical post, so feel free to skip it if you're not interested in content creation for latter versions of DAZ Studio.
What rigidity actually does is affect the degree to which generated FBMs affect a clothing mesh. The DAZ documentation is here: docs.daz3d.com/doku.php/public…
I find this a bit puzzling inasmuch as what it suggests rigidity be used for - the center ring on a bikini, buttons, buckles, clasps - is exactly what I've found it hardest to get good results with using the feature.
The issue is that for smooth and continuous deformation, the rigidity group needs a good set of reference faces around it, and it seems to need them to be continuous with the "rigid" verts. So something fully discontinuous, like a discreet submesh (as most buttons and buckles must be) is going to work poorly.
What I've found it more useful for is in creating a basis for FBMs. So if you create a rigidity map, then dial in a generated morph, then export that as an obj, you can get a much better morph basis than starting from just the generated version. Custom FBMs override the effects of a rigidity map, so this is not for nothing.
What I'm experimenting with now with regard to this is threefold:
1. The area between and just under the breasts, to prevent unwanted creasing (in those items where creasing is unwanted; I'm well aware some people like, and want, the cling effect, but I generally do not).
2. Lower portions of long tunics or skirts, perennially creased and distorted on larger or more greatly deformed morphs (no skirt will EVER look right on a generated BodyBuilder morph, for instance).
3. Outliers of a mesh that are significantly away from the body, like dangling sleeves on a gown, long tails or trains, etc. This saves a lot of trouble trying to un-distort these when making a "real" FBM of a generated one.
Other uses for the feature may unfold as I explore it in more detail. One never quite knows, which is one of the delights of getting into a program like DAZ Studio.