by joepal » Sat Sep 11, 2021 3:35 pm
Without knowing how your mesh looks, these are the possible causes:
1. Clothes vertices have been matched suboptimally with body vertices. This happens when you have a single vertex group for all vertices (in this case probably "body") or go with the default "left", "mid", "right" groups. In difficult areas, you might need to help the matcher along by assigning more detailed vertex groups on the clothes and on the body ("left_crotch", "outer_left_thigh"...)
2. It might be caused by too little geometry. There is not enough geometry to cater for a proper deformation. From the image, this does not to be the case in this instance though.
2. It might (kind of counterintuitively) be caused by too dense of a geometry. There are too many vertices, and they bunch up when you deform the body and squeeze them together.
But in general, it is not surprising that deformations look a bit strange on the first attempt. In difficult areas and in certain poses, the clothing might need a bit of tweaking in regards to both geometry and vertex matching to behave optimally.