offset curve problem

I have an interpolated curve that I am having problems offsetting.

This may be (and hopefully is!) an easy fix.

The curve is in a helix like shape and is driven by 4 modifiable vertical rhino splines.

when the interpolated curve is a shorter height, the offset works fine:

however once the interpolated curve is increased in height the offset curve fails to offset beyond a certain height:

has anyone had this problem before??
Any help would be greatly appreciated
files are attached

Attachments:

helixthroughcontours03.3dm, 57 KB
helixthroughcontours03.ghx, 299 KB

Replies to This Discussion

Permalink Reply by kleerkoat on November 13, 2009 at 5:55am

I'm not a Grasshopper pro, but I've spent a lot of time using offset curves and it happens to me all the time. Usually I just have to play with the offset a little bit to get the whole curve to appear. I'm usually doing the distance with a slider so it can be a matter of sliding the distance by .001" to get it to appear.

There seems to be some values that it doesn't like, so like I said, I just slide it plus or minus my target distance just a little bit and it will generate it.

Also, I'm not sure if this helps, or even what it does but if you right click and toggle Reparameterize sometimes it helps.

Hopefully someone can give you better help than me, as I'd like to know why it does it also.

Permalink Reply by David Rutten on November 13, 2009 at 8:34am

I don't know why this would happen either, but I do know that curve offsets are essentially planar operations. When you are offsetting a curve which rolls and tumbles in 3 dimensions, the offset algorithm probably gets confused.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by kleerkoat on November 13, 2009 at 11:15am

Hey David,

I've only ever used it for 2d curve offsets and it does it.

But like I said, I can adjust the offset by a small amount and then it works, it's very weird. Like I can slide the input to .0787 and have some of the offset disappear, but if I change it to .0789 it will offset correctly. Those are just made up numbers, they are just to show how small of a change it can take to make or break the offset.

Ryan

Permalink Reply by David Rutten on November 13, 2009 at 11:53am

Well, if it also happens in pure 2D cases there is something even worse wrong with our algorithm. I'll ask the math guys in Seattle for an offset function that works better when it's used without a point-pick hint.

--
David Rutten
david@mcneel.com
Poprad, Slovakia

Permalink Reply by jeffer on November 13, 2009 at 3:54pm

Thanks guys, I tried to adjust the offset distance and toggling the reparameterize. Haven't had much success yet. Is there a workaround either of you can think of?

I'm basically trying to build a ramp from the first interpolated curve. Maybe using curve frames will work? I'm not quite sure how to align the frames so that the ramp is always flat though.

Any ideas would help.

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