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Bounding a Spline
Read 2117 times
* August 05, 2009, 12:46:24 PM
I need to draw a spline where I need to define 3 points: start and end and the location of the maximum width.

See attached.

The problem is that the plain vanilla spline causes the spline to bow out beyond the limit point.

Is there any simple way to have the curve stay within the line? I try inserting new point and I get new bowings.

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* August 05, 2009, 12:52:36 PM
#1
"Spline by Fit Points" will do the job using just three points.

Henry H

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* August 05, 2009, 06:22:31 PM
#2
I am using spline by  fit points. The problem is that the curve extends past the fit point in the middle.

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* August 05, 2009, 08:13:19 PM
#3
I am using spline by  fit points. The problem is that the curve extends past the fit point in the middle.

Not sure what I'm missing here, cuz I don't see your curves extending beyond the green boundary lines.

Henry H

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* August 05, 2009, 10:52:22 PM
#4
I am using spline by  fit points. The problem is that the curve extends past the fit point in the middle.

The only thing I see extending past the green boundary is a node when the Edit Tool is set to "Edit Control Points". The nodes for "Fit Points" are within the boundary and in either case, so are the splines.

Staring at this a little longer, I think I see where the spline goes past the boundary by a wee bit. One has to zoom way in to see it. I don't think there is a cure.





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John R.

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* August 06, 2009, 10:18:00 AM
#5
The reason it needs to be bounded it that these will be parts of a loft. When the width is off slightly, you get a wavy side, rather than straight.

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* August 06, 2009, 07:32:34 PM
#6
Reported distance between the boundary lines is 2.25" and the reported width of the pair of Splines is 2.2512341459", even though the reported distance between the middle nodes is 2.25". Don't know how one could draw these entities as Splines and have them come out exactly correct without rather laborious post-editing. BUT it's pretty easy to make them as Beziers. After creating the Bezier by snapping on the three defining points, select it with the Edit tool and place the green rotation handles of the middle node directly on the boundary line (using "N" SEKE). I drew one Bezier this way and then mirror-copied it, and the reported width of the pair is precisely equal to the distance between the boundary lines.

Henry H

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* August 12, 2009, 09:32:29 AM
#7
I am suprised at how difficult this apparently simple problem is.

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