Offsetting a single span curve


I’m trying to model the stem of an ocean liner and I need to offset the curve exactly 13.50 inches. However, when I do so, I go from a beautiful single span curve to a messy curve with far too many points. If I try to rebuild it, it deviates too much from the original curve and therefore it isn’t accurate anymore.

So, to my question: is there some way that I can get the same curvature as my main single span curve but with an offset or is rebuilding with a lot of deviation the only option?

Sorry if it’s a stupid question. I am new to this.

Thanks in advance.

Hello - you can try this:
first offset, then offsset with the Loose option, then adjust the control points on the loose offset to get the curve as close as possible to the ‘true’ offset. PointDeviation can help while adjusting. In general, accurate offsets of arbitrary curves - i.e. not arcs or lines for example - are always more complex than the input.



Like Pascal said, offset to get the accurate multispan first then manually create a new single span to match the best you can (lots of fiddling around with control points).

It may be easier to copy your single span over to the offset curve and scale it up for starters. Then change the degree using ChangeDegree command.

Usually you’ll have to increase the degree by two (compared to the original single span) to get a good match (or one if it’s a very simple curve).

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Thank you very much for the help! I will give it a try tomorrow and see how it fairs. :slightly_smiling_face:

Oh…one more tip…

Try out the command EndBulge to adjust your new single span after you’ve scaled it and made sure the ends are in the correct place. Use the Curvature settings in the command window (if you want to keep curvature that is… ).

Good luck!

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Thanks a bunch! All of this helped in achieving what I wanted.

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I like this method too-

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That’s a great one Kyle! It works great for closed curves but in my case I can’t get it to match the other curves around. One side gets to G2 but the other remains at G0 even though the original curve is G2. It deviates too much when I try to match it.