Curvature issue

Hi guys, I have a small problem with this surface. I’m trying to replicate a folded sheet (image attached), but I can’t get a good continuity: the zebra is very concentrated in the central part, I would like it to be more distended (it becomes very visible when I render with a metallic material). I also attach the 3dm file. I am using the “surface from network” tool, should I use another one?

Can anyone help me?

Folded sheet.3dm (563.1 KB)

Hi Marco - I tihnk it will be hard to mimic paper but I would start with curves that are all the same length and then trim the rounded corners after the fact:


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use _length to query the current length, then scale the curve
you can use inline math for the scale factor

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…
(@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…)

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

Anyway I don’t think that the exact lenght is the problem. How would you do this form? Surface from network or loft (with only curves in one direction)?

Thank you! I am trying to do that. It’s not that easy, it’s my first time with this method. I didn’t get how to use _flowAlongSrf… I tried in different ways but i am not understanding what i need to click and in which order

there should be some tutorials around.
google search rhino flowalongsrf tutorial…

or - my favourite
try to rebuild those small examples from the help