Match the same points constellation of set off curves with their originals

Always wanted to know how to do this the easy way. From what I know you can FitCrv but it would end up with two many points in the ‘child’ curve (offset) — any ideas to match them with the same point count and overall shape?

Maybe copy the original and scale it down?

Look at this video from Dave

Hi Hannes - the long way is to make a line, perpendicular, of ‘offset’ length at every curve edit point (not control point) then move copies of edit points to the ends of the lines. Same general shape…

-Pascal

Hi Hannes,

FWIW
In addition to other replies, try what it gives you to run RebuildCrvNonUnifirm with both curves selected.
http://docs.mcneel.com/rhino/5/help/en-us/index.htm#commands/rebuildcrvnonuniform.htm#kanchor1832
They will become equal in pointcount wich is good for lofting and such.

-Willem

Hey @jordy1989 the video is unf only applying for the symmetrical curves only.

I think the only way to do this consistently well is the @pascal way from what I know until know. Pascal could you consider a script for this for the future? Thanks you all, Hannes

@pascal found out that this won’t match the shape. Maybe this is why there are so many control points :smile:

Yes, that’s why offset adds points, it needs them in order to maintain even spacing. Depending on the curve, offsetting control points can be relatively close to a real offset, or nowhere near…

–Mitch

This is what bugs me about offset though, is that the offset curve is often a lot more complicated than it needs / should be. For instance in the attached, over here if I offset this curve, which is 3 point 2 degree, 0.25 units using the default .0001 tolerance for this file, the result is a 7 point 3 degree polycurve, which explodes into two 4 point degree 3 curves. If I rebuild the resultant 7 point degree 3 polycurve to 3 points degree 2, Rhino reports it can do so with a maximum deviation of 1.81691e-05, which is about 5 times smaller than both the file and the offset tolerance. So in a case like this, why is the offset so messy? Or am I missing something?

OffsetEx.3dm (233.0 KB)

Thanks,
Sam

Thinking about a ‘loose offset’ command. with same control point location. could not someone script something like this??? :slight_smile:

Ok, I was looking for something along these lines today - I offset two curves that are also curved in the Z direction. Upon offset, the "outside of the OFFSET original curves are not in plane with the originals in the Z direction.

After a few minutes I remembered the project command - which I use a lot - and decided to create a vertical plane and project the curves onto from a front view. Then I created a plane in the X-Y direction using those original curves. Then I projected the offset curves onto the surface which I had used “extend surface edge” on all edges - and it matched the original curve in the Z direction.

After projecting I can see from a front view that they are once again - original and offset curves - in the same Z. Not sure if this is what you were looking for, but it worked fine for me.