starting to learn VB, point on curve (

having a bit of trouble in VB finding the right way to find a point on a curve based on a length instead of a number between 0 and 1. i guess i'm looking for the vb equivalent of the evaluate by length component instead of by paramter.

thankyou

Replies to This Discussion

Permalink Reply by David Rutten on December 31, 2009 at 3:50am

Hi William,

There is no function for this, unless you're willing to use the RhinoDivideCurve() function which gives you potentially many points and thus might take a long time.

What you have to do is figure out the parameter along the curve at that length, and then use that parameter in conjunction with Curve.PointAt(t)

You can find this parameter with the OnCurve.GetNormalizedArcLengthPoint() function. The word "arc" in that name has nothing to do with circular arcs, so it's a confusing name. Also note that the function doesn't work with physical lengths, but with relative lengths. So if you want the parameter exactly one quarter along the total length of the curve, your s argument is 0.25.

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

Permalink Reply by David Stasiuk on January 1, 2010 at 10:06am

Here's some code that evaluates the length of the input curve, and then calculates the "T" value based on the length you input. It's really simple...I've also added an "IF" statement that requires the length to evaluate be less than the curve length.

All it does is calculate the "T" by dividing your desired distance by the total length of the curve.

Private Sub RunScript(ByVal Input_Curve As OnCurve, ByVal Distance_On_Curve As Double, ByRef A As Object)

Dim dblLength As Double
Input_Curve.GetLength(dblLength)

If Distance_On_Curve <= dblLength Then

Dim dblTParameter As Double
dblTParameter = Distance_On_Curve / dblLength

Dim pntCurve As New On3dPoint(Input_Curve.PointAt(dblTParameter))

A = pntCurve

End If

End Sub

Permalink Reply by Guga on February 20, 2011 at 10:31am