Knife Project (projected text) is not transforming with the mesh I have made a simple butterfly animation and projected the text “B”on one of the wings.
However when the wings flap, half of the text mesh gets left behind. (see my attached file, dropbox link).

What have I forgotten to do, or does knife project not work in animations?

https://www.dropbox.com/s/k7tkborcmd9v82n/butterflyText.blend?dl=0
It's just a vertex weight problem, I think, perhaps because 'Automatic Weights' doesn't cut it, here.



If the vertices illustrated above are assigned with weight 1 to the groups tri_R, main, and tri_L respectively, everything seems to work.

Maybe select vertices in  Edit Mode in a wireframe view, to ensure you get them all, and assign to groups with weight 1 in the Data > Vertex Groups panel, rather than painting, in this case.