Trying to figure out why these curves won't split

So, I’m trying to diagnose why the curves in split_failure.3dm don’t split.

I’m trying to split the periodic curve with the open curve, and I get the error “Split failed, objects may not be within tolerance of one another.” I’ve snapped the end of the open curve to the periodic curve using the near snap, so they should be within tolerance. I made sure that the periodic seam is well away from the curve intersection. If I put a point on the open curve’s end snap, that point can split the periodic curve without issue. I tried rebuilding the curves to see if that would help anything, but it didn’t. I also tried Rhino 4 and Rhino 5.

Any ideas?

Hi Tom,

if i understand this correctly the open curve cannot split the closed curve because there is only one intersection point. If you intersect both curves and try to split the closed curve with the intersection point, it will not split for the same reason. Are you expecting that the open curve is split at its start/end point automatically ?

With a circle and a point on the circle it results in the same behaviour.


Thanks clement, that helps a lot. I was trying to narrow it down to the simplest possible case, but it looks like I got too simple… :slight_smile:

You can move the curve seam to that point using crvSeam but I’m at loss on how to open the curve, @pascal?

You can’t split closed curves at one point - you never have been able to… You need a minimum of two points. You cannot “open” a closed curve by splitting it at one point either, by definition, when the curve start and end points are the same, the curve automatically gets defined as closed. (AFAIK)


Hi Ricardo- There is TestSeamOpener, but it moves one of the end points…


A work around is to draw a polyline through NOT ONLY the place you wish to split BUT ALSO through another place on the same curve. Split it, turn on points, SEPARATE them where you want them separate, select the two pieces then JOIN.

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