Grasshopper

algorithmic modeling for Rhino

Shouldn't it be 0 to 1?

F.

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Is the curve closed? Can you post it?

Yes it is a foil profile.

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It being closed makes sense then. If divide produced points at param 0 and param 1 on a closed curve, you'd always wind up with a duplicate point at the curve seam. With an open curve, you would expect to see the params go from 0 to 1. There are other differences in behavior - dividing an open curve by N segments, you get N+1 points whereas with a closed curve you get only N points. 

Sorry Andrew, but if I read right, N is the number of segments, so I should expect N+1 points in any situation. That's not the case. I asked for ten segments and I got nine.

If you then plug a polyline component, the result will always be open. Isn't that inconsistent?

If there is a good reason for this, please explain again.

I mean, there IS a point at t=1... What's wrong with a duplicate point?

I asked for ten segments and I got nine.

You didn't get any segments actually, they are implied to exist in between the points (and parameters) you do get. When the curve is closed, the component simply omits the last point (as it would be coincident with the first one). The Rhino _Divide command works in the same way.

Thanks David.

You're saying that it's not a bug, but a feature?

I know how the divide command works in rhino, and the Curve.DivideByCount method.

(including the MarkEnds / includeEnds option). I understand why duplicate points are an issue in Rhino, because the order in the list is irrelevant.

My point is : is it the behaviour we expect in grasshopper?

Now I changed my mind, I don't want points anymore, but perp frames.

On my foil profile (which has a kink at the start/end), the first and the last planes are not the same! Yet it behaves in the same way.

Yes it is designed this way. I assumed that one wouldn't want the same point twice when dividing a curve up. I can see though that sometimes you do want this and then you have to jump through a bunch of extra hoops.

Ok sry for being a nuisance

Sorry there's no easy way to do what you need to do...

Hi Fred, I think I might have something related lying around. It's an oldie so I'm not entirely sure it'll fit or contribute to your goal, but it reminded me of the trailing edge issue when using airfoils.

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