### Perpendicular Vectors

Demonstrates how to calculate a vector that is perpendicular to another vector using RhinoScript.

VBScript

' Description:
'   Returns a 3-D vector that is perpendicular to another 3-D vector.
' Parameters:
'   v - the 3-D vector to evaluate.
' Returns:
'   A perpendicular 3-D vector if successful, Null otherwise.
' Remarks:
'   The result is not a unitized 3-D vector.
'

Function GetPerpendicularVector( v )

GetPerpendicularVector = Null
If Not IsArray(v) Or UBound(v) <> 2 Then Exit Function
If Rhino.IsVectorZero(v) Then Exit Function

Dim i, j, k
Dim a, b
k = 2
If Abs(v(1)) > Abs(v(0)) Then
If Abs(v(2)) > Abs(v(1)) Then
' |v(2)| > |v(1)| > |v(0)|
i = 2
j = 1
k = 0
a = v(2)
b = -v(1)
ElseIf Abs(v(2)) >= Abs(v(0)) Then
' |v(1)| >= |v(2)| >= |v(0)|
i = 1
j = 2
k = 0
a = v(1)
b = -v(2)
Else
' |v(1)| > |v(0)| > |v(2)|
i = 1
j = 0
k = 2
a = v(1)
b = -v(0)
End If
ElseIf Abs(v(2)) > Abs(v(0)) Then
' |v(2)| > |v(0)| >= |v(1)|
i = 2
j = 0
k = 1
a = v(2)
b = -v(0)
ElseIf Abs(v(2)) > Abs(v(1)) Then
' |v(0)| >= |v(2)| > |v(1)|
i = 0
j = 2
k = 1
a = v(0)
b = -v(2)
Else
' |v(0)| >= |v(1)| >= |v(2)|
i = 0
j = 1
k = 2
a = v(0)
b = -v(1)
End If

Dim rc(2)
rc(i) = b
rc(j) = a
rc(k) = 0.0
GetPerpendicularVector = rc

End Function