Hi @nougat time ,
| “is there no way to tell the SubD Modifier “hey here´s a UV Seam, don`t move that”?
No, you are right, that Edge Loops can only be constraint by ‘Holding Edges’. How far away those ‘Holding Edges’ are, influences how far the original Edge Loop can move around; which also means, how much smoothing is done by the Subdivision Surface algorithm, or how sharp the Edge loop becomes…I’d recommend using two ‘Holding Edges’ one on each side and if possibly evenly spaced…again: how far away from the (in your case) Seam, decides how much or little smoothing will happen.
Not moving the Edge Loop at all, also means not smoothing it and therefore it stays as sharp as without the Subsurf. (it doesn’t sharpen it; it already was that sharp…)
Basically, what you are asking for, is that the Seam doesn’t move, but still gets smoothed, which sounds like a contradiction to me.
