I would suggest another workflow.
your surface has to be developable - you ll find a lot about this in the forum.
if it is developable, it is a special case of a ruled surface.
so there have to be ruling lines.
(red in the screensho)
- one is given at the bottom by your folding
- a second is defined by the symmetry
with this background
just draw half of the paper first, then mirror
draw a curve that defines the shape (blue)
_extrudeCrvToPoint will give an initial surface
_extendSrf to make it big enough…
_unrollSrf
(@pascal _unrollSrfUV gives a strange triangular result in this case - why ?)
_rectangle or _boundingbox to mimic the rectangular sheet
_flowAlongSrf to get the curves from the flat to the curved surface (with some tolerance…)
_trim
_mirror
additionally if you unroll the surface, the lower corner must be 90 degree.
I just did a rough visual approximation …
this approach will give you nice curvature continuity with less work…
Of course you could do some physic simulation with grasshopper / kangaroo, but this would be more work to do…
Folded sheet_tp.3dm (255.8 KB)
hope this helps - kind regards -tom