at inspection, you'll see that the trims are tubes which geometrically intersect with the edges of the dress, but they have no vertices or edges in common. Distances between vertices are too larges, welding is never going to work.

The solution to this particular case is to select the trims into the soft decorated groups

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though