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' ParametricEllipse.rvb -- February 2012
' If this code works, it was written by Dale Fugier.
' If not, I don't know who wrote it.
' Works with Rhino 4.0.
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Option Explicit
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' ParametricEllipse
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Sub ParametricEllipse()
' Semi major and minor axes
Dim a : a = 6.0
Dim b : b = 3.0
Dim c : c = 4.0
' Domain of ellipse
Dim t0 : t0 = 0.0
Dim t1 : t1 = 2.0 * Rhino.PI
' Number of parameters to sample
Dim n : n = 22
' Array of calculated 3-D point
Dim pts()
ReDim pts(n)
' Domain of samples
Dim u0 : u0 = 0
Dim u1 : u1 = UBound(pts)
' Calculate ellipse points
Dim i, t, x
For i = u0 To u1
x = NormalizedAt(u0, u1, i)
t = ParameterAt(t0, t1, x)
pts(i) = PointAt(a, b, t)
Rhino.Print Rhino.Pt2Str(pts(x))
Next
' Add elliptical curve to Rhino
Call Rhino.AddInterpCurve(pts, 3, 3)
For i = u0 To u1
x = NormalizedAt(u0, u1, i)
t = ParameterAt(t0, t1, x)
pts(i) = PointAt(c, b, t)
Rhino.Print Rhino.Pt2Str(pts(x))
Next
' Add elliptical curve to Rhino
Call Rhino.AddInterpCurve(pts, 3, 3)
End Sub
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' PointAt
' Evaluates an ellipse at a parmeter
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Function PointAt(a, b, t)
Dim pt(2)
pt(0) = a * Cos(t)
pt(1) = b * Sin(t)
pt(2) = 0.0
PointAt = pt
End Function
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' ParameterAt
' Converts a normalized parameter to an interval value
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Function ParameterAt(t0, t1, x)
ParameterAt = (1.0 - x) * t0 + x * t1
End Function
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' NormalizedAt
' Converts an interval value to a normalized parameter
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Function NormalizedAt(t0, t1, t)
Dim x : x = t0
If (t0 <> t1) Then
If (t = t1) Then
x = 1.0
Else
x = (t - t0)/(t1 - t0)
End If
End If
NormalizedAt = x
End Function
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