Straighten a curved polysurface

Hello, I am looking to straighten a curved polysurface. Essentially I modeled a cuff bracelet that I wan’t to straighten out completely. I tried the bend tool but that doesn’t seem accurate at all and distorts the model way to much. Any help is much appreciated. Thank you.


Hi Brandon - try this:
(from the file you posted on Tech)

ExtractSrf (copy=Yes) the inner surface.
ShrinkTrimmedSrf, then UntrimBorder
You’ll have the ‘raw’ inner surface… Now UnrollSrfUV (maintains the UV parameterization)
Then FlowAlongSrf from the 3d surface to the unrolled one.

Unroll.3dm (832.4 KB)


Hey Pascal, thanks so much. That definitely worked. My only issue is that it seems that when the inner surface is unrolled it isn’t long enough. What I did previously was 3D print a curved model and then straighten it out flat with heat. When I measured the model it was a 6mm difference from the unrolled inner surface, In the Unroll.3dm file you attached it also seems like the curved model would be slightly larger then what the unrolled inner surface comes out to. Is it possible that it is slightly undersized? Thanks again for the help.

Hi Brandon - here it looks like my example is slightly short

Length = 60.536 millimeters

Length = 60.514 millimeters

Scale1D the flattened surface to the correct length before FlowAlongSrf.


Is there anyway to get a more accurate unrolled surface? I guess in theory I can print out a 1-1 version, take a string to the interior and measure with a caliper what it would be.

Well, I think you want the length to match the 3d surface - in this case it is a simple fix… Scale1D, snap to an end on the surface, then snap to the other end and then type in the length (Length command,previously noted down) of the corresponding edge of the 3d base surface.


Right. My only issue is that I only have the curved 3D model to reference. So if I wanted to get a real life measurement of the curved surface I would have to print out each model and then straighten and then go back and Scale1D to the exact length. That’s neither here nor there though. I am going to print out a 1-1 scale and measure then go back and Scale1D.

Anyway, thanks so much. This saves me from a big headache. I have received help from you in the past and you certainly know your stuff. Thanks