In the attached file, unrolling the right-hand surface (top view) produces a mutant surface that looks like it might be folded in half (left-hand surface). 'Same thing when I use smash.


Tags: UnrollSrf

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No problem unrolling the windshield 


That does look right. Which version of Rhino are you using? I'm using Rhino 4. I wonder if it got corrupted somehow.



'Just checked to make sure I'm up-to-date on service releases, and I am. Unfortunately, the SR install program will not let me reinstall on top of the same SR that I'm already using.


'Just uninstalled Rhino and reinstalled up to RH4SR9 (starting from the original CD, ugh!) and got the same erroneous results. Oddly, the shape of the unrolled surface also depends upon the XYZ position of the original, but none is correct (per the image posted by STEELFISH SLOEPEN).


If I first do a "Refit to Tolerance" on the windshield surface, the unroll works correctly. So I guess my question now is, "What was wrong with the original surface that made it unroll so weirdly?"



Phil i use 5, forget 4 , what whas wrong?? sometimes just a little twist or irregularity in the surface, working very neat with snaps is the solution. dont worry to much and go on i sometimes have a very long shipssurface wich wil not unroll for some unexplanable reasons,   i now mostly do a test unroll befor a complete the hull.....

Regards John

Hi Phil- V4 makes a mess of this, clearly a bug... So far I ahve not found a good workaround other than FitSrf that you mentioned. V5 does the right thing with this.


Thanks, Pascal. I probably should upgrade to RH5, but I'm not sure my 3.2GHz, 2GB WinXP machine is up to it.


try a test version ?

Done, and upgrade on order!

I do notice in RH5 that, if a compound polysurface is unrolled without exploding, the individual pieces can overlap. IOW, the points (or angles) at which they are joined do not seem well-chosen.


didnt realise i can unroll without exploding

Yes.  Not all polysurface structures CAN be unrolled in one piece without overlaps - just like not every form can be made in sheet metal out of just one piece. So often you need to separate complex polysurfaces in several pieces.

However, it's true that Rhino does not always choose the optimum seams to leave joined, it seems more or less by chance - I don't know how the algorithm works actually - maybe it starts with the face at index 0 and unrolls outward, no idea...

You can "help" Rhino unroll a polysurface correctly by using the command UnjoinEdge at judicious locations before unrolling, that will say to Rhino "do not leave stuff connected here".




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