Grasshopper

algorithmic modeling for Rhino

Hi everyone! I'm having some trouble offsetting a curve, basically because its topology is changing (e.g: it has more points and segments after the offset operation) and that is giving me problems with a loft operation later on. 

I've read some topics in the forum regarding offsetting, but it seems that no one have had this problem (very surprisingly I'd say). 

This is what I'm doing: 

a) I have a non-convex,  closed polyline in the XY plane (the native curve being referenced from rhino). Let's call it CURVE A

b) I rotate and move CURVE A to a different plane (obtaining CURVE B). 

c) I offset CURVE B, and now it has more segments and points than CURVE A (basically, it creates the segments that would be required to close the shape if it had been offset segment by segment instead than as a whole)

d) when I loft these curves - CURVE A and CURVE B, it gets messy (since the different curves have different segment count)

I've tried a lot of workarounds:

1 - Offset CURVE A on XY a certain amount, and then offset it back, obtaining CURVE A 2.0. It doesn't work, since CURVE A and CURVE A 2.0 have the same topology, so the final loft is still messy

2 - Offset CURVE A on XY without offsetting it back: It works, but I need to maintain the original shape at the base of the resulting surface (after the loft operation described earlier). I thought that just scaling the resulting brep would do the trick, but then I realized it doesn't. 

3 - Using CURVE B (the curve that later will be lofted with CURVE A) to finds its closest point on CURVE A, and then re-creating the original curve with this new points (CURVE A 3.0): Doesn't work on all cases... 

So that's it I think. I'm really lost with this, so any help will be very much appreciated. 

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I found the "Reduce Polyline" component, and it is doing the trick in most of the cases. Anyway, since it is a manual override, I still would like to know if anyone has dealt with this before, to see if there is a better workaround to this issue. 

I think "offset loose" will preserve the control point structure of your input curve.

Man, I feel like a fool. How is that I didn't see that before?? Maybe because it's my second night in a row without sleeping (damn finals!).

Thanks a lot Andrew, I'll try it!

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