ArchimedeanSpiral.rvb

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' ArchimedeanSpiral.rvb -- June 2008
' 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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' Creates an archimedean spiral.
' Change 'a_const' to turn the spiral.
' Change 'b_const' to control the distance between turnings.
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Sub ArchimedeanSpiral()

	Dim a_const, b_const, step_angle, num_points
	Dim curr_angle, base_point, radius, points(), i
  
	Rhino.Print "Archimedean Spiral: 'Radius = A + B * Theta'"
  
	a_const = Rhino.GetReal("Value of 'A' constant", 1.0, 0.01)
	If IsNull(a_const) Then Exit Sub
    
	b_const = Rhino.GetReal("Value of 'B' constant", 1.0, 0.01)
	If IsNull(a_const) Then Exit Sub
    
	num_points = Rhino.GetInteger("Number of points to calculate", 10, 2)
	If IsNull(num_points) Then Exit Sub

	step_angle = Rhino.GetReal("Angle between points", 30.0, 1.0, 45.0)
	If IsNull(step_angle) Then Exit Sub

	curr_angle = 0.0
	base_point = Array(0.0, 0.0, 0.0)
	ReDim points(num_points - 1)
  
	For i = 0 To UBound(points)
		radius = a_const + (b_const * curr_angle)
		points(i) = Rhino.Polar(base_point, radius, curr_angle)
		curr_angle = curr_angle + step_angle
	Next
  
	Rhino.AddInterpCurve points
	'Rhino.AddPoints points

End Sub