can someone help me unroll this surface so it looks like a Tensile test sample. The wider edges on the top and the bottom.
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maybe post your file?
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It’s a polysurface and not just a surface…
You can unroll strips in either of the two directions.
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what do you mean by that Martin? Im new to all of this 
cant i juat unroll the whole surface?
Donut_sechstel_einzel v1.obj (260.1 KB)
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i importes as a mesh and than i used MeshToNURBS to make it a polysurface but if i use unrollSrf it just unfold every faces by itself
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Then…
One of the squares you see is a surface. When everything is joined, you may have one or multiple polysurfaces. Polysurface means multiple surfaces…
You can actually also unroll the whole thing but some of the edges have to be unjoined.
The *.obj file appears to be empty.
Please post the Rhino file
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The Explode option in UnrollSrf controls if a polysurface unrolls as separate surfaces (Explode=Yes), or as a single polysurface (Explode=No).
Portions of the object has double curvature, similar to a sphere. UnrollSrf only works on objects which are (or close to) “developable” which means they have single curvature, similar to a cylinder or cone.
Flattening the object will require some distortion: stretching, compressing and/or shearing. That is how basic geometry works.
Try Squish Squish | Rhino 3-D modeling or Smash Smash | Rhino 3-D modeling (mcneel.com) to flatten the object with distortion.
MeshToNURB simply replaces each mesh facet with a simple NURBS surface. The number of surfaces is the same as the number of mesh facets. For an object like this one it is possible to create a new NURBS model of the same shape which is much simpler.
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i dont know how you got to that result without changing the topology at least once, you might have exported it differently in your file or used Rhino already? either way in Rhino you can do that with QuadRemesh, with a low quad count, check detect hard edges and convert to subd.
using the command ToNURBS will result you in a single surface like so if that is what you need or can use.
you can use SrfSeam and adjust the seam it is where the surface will be split for unrolling and UnrollSrf did not even make any noise and presented me with this result. maybe the command was improved but usually for more complex surfaces you would indeed need Squish as David suggested. Smash is an older version of Squish as far as i know, Squish gives you also more options and also pairs with the command SquishBack.
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that is exactly what i was looking for!!! thank you so much
but if i use UnrollSrf there is a error “At least one surface you are trying to unroll is not developable because it is doubly curved.
If you want to unroll it anyway, try using the Smash command or adjust the relative tolerance on the UnrollSrf commandline.
Unrolling doubly curved surfaces will produce inaccurate results.”
not sure, i like lowering the tolerance on this command which will unroll stuff that usually does not, maybe i had it set to something loose from some earlier meddling, not on my computer now cant double check, but be aware if you do that the result might not be so accurate maybe try squish instead
I’m also curious how that happened, because that looks like a double curvature surface…
ok guys i looked at it once more, it seems my relative tolerance was set to 0.5 which is pretty high, as said previously a higher tolerance will make your surface unroll. i am not sure which one produces the better unroll, unroll set to a loose tolerance or smash, with squish you can adjust your preferences of course.
for UnrollSrf to work here you have to use the dashed version (-UnrollSrf) to adjust the tolerance, in v7 that was not necessary if i remember correct, but whatever.
i actually got a message, the surface is smaller, you can also adjust the warning in the dashed version.
Area is 134.0624 sq millimeters (7.86 % ) smaller after unrolling
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do you know why the upper part of the unrolled element is kind of twisted. there is not a straight edge on the upper part
i have no idea in what you are seeing and where. if you have managed to progress then please be so kind and post what you have so far that we can have a look. people are very helpful but we are no clairvoyant wizards.
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