Offset Bug

Offsetting this curve with a distance of 6 mm returns a wrong result.

201204 Offset Bug.3dm (99.8 KB)

I don’t see this as a bug. There are two things you can do to improve the offset.

  1. fit a curve with a higher degree with FitCrv
  2. if your green curve had a short straight segment in between arc and line, the offset command has something to offset. Without this short segment, how should the offset command know what to do?

201204 Offset problem.3dm (345.1 KB)

What do you mean, not a bug?
The description literally says:
The Offset command copies a curve so that all locations on the copied curve are a specified distance from the original curve.

Dunno, I appear to get a reasonable offset here (V7)… what am I doing differently?

Your image doesn’t look like the drawing I uploaded, compare it to my image in the original post. Not sure what went wrong but your green curve looks smoothened/crappy.


All I did was open your .3dm file above and call Offset. Didn’t do anything else…

@Helvetosaur, maybe your offseting the wrong curve?

Maybe - are you offsetting the green curve to the outside or the black curve to the inside?

The other end of the curve with just 4 mm offset.

Green to outside, I guess I should have made that clearer

6 mm offset is larger than the radius of the curves

OK, my bad.

Yes, exactly. What do you expect to happen in a corner like this?

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Still, the part where the distance is 3.92 (in the image opening the topic) seems less than optimal for this situation.

I understand that this might be a hard problem to solve from a mathematical/coding perspective. But it’s still a bug.

I expect it to do whatever any graphic software does to solve this:

Or this (with rounded corner setting):

You understand that this curve does not have a constant distance of 6 mm either?

In the sharp corner example, yes. In the round off corner example, no.

I agree, it should probably just fail if the offset cannot be made correctly.

We all know that Offset is unreliable in Rhino, this is just another case - and often it comes down to not being able to 'improvise" and throw away a segment which it cannot offset and try to connect the ones next to it.

This is akin to filleting surfaces with radii larger than will fit in a corner. There are ways to improvise, but Rhino just doesn’t know how.

I actually would prefer an incomplete curve in this case. (not quite sure if this is what you wanted to say too)

Incomplete curve, or some kind of notifying the user that the distance is not everywhere as requested

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Hello - here is what I get from V7 - one end cuts the corner but the distance is consistent. The marked end of the curve does not have the short straight segment and offsets differenly.

201204 OffsetLessProblem.3dm (235.5 KB)