Imports System.Math

Public Class Form1

    Public Structure xyzType
        Dim x As Double
        Dim y As Double
        Dim z As Double
    End Structure


    '/==================================================================
    '/ function rotateKoordinates(axis, rotation, xyz) as xyzType
    '/ Returns (0, 0, 0) when stuff goes wrong.
    '/
    '/ 20080509 Jens
    '/ This function returns the coordinates of an object that has
    '/ been rotated around one axis in a coordinate system.
    '/ The function assumes that you rotate the object counter clockwise
    '/ as viewed from the positive end of the axis you rotate around.
    '/ This function is for VB.NET and it does need one structure to be
    '/ declared:
    '/ Public Structure xyzType
    '/   Dim x As Double
    '/   Dim y As Double
    '/   Dim z As Double
    '/ End Structure
    '/
    '/ You provide information about what axis you want to rotate around,
    '/ how many degrees you want to rotate and the x-, y- and z-coordinates before
    '/ the rotation.
    '/ The function returns the new coordinates for the object.
    '/ This can also be used if you let the object be fixed and
    '/ instead rotate the coordinate system clockwise around the provided axis.
    '/
    '/ Example; A vector (0, 3, 0) rotates 90 degrees counter clockwise
    '/ around the z-axis as seen from the positive end of the z-axis:
    '/ (z, 90, 0, 3, 0) => (-3, 0, 0)
    '/------------------------------------------------------------------
    Public Function rotateKoordinates(ByVal axis As Char, ByVal rotation As Double, ByVal xyz0 As xyzType) As xyzType
        Dim xyz1 As xyzType
        Dim pi As Decimal : pi = 3.1415926535897932384626433833D
        Dim radianer As Decimal, length As Decimal
        Dim alfa1 As Decimal

        xyz1.x = 0
        xyz1.y = 0
        xyz1.z = 0

        'In case somthing goes wrong at least return (0, 0, 0)
        'This is questionable, but a philosophical question.
        rotateKoordinates = xyz1

        'If no rotation or any whole number of complete
        'rotations, don't waste time computing the
        'obvious. Return what was sent to the function.
        If (rotation Mod 360) = 0 Then
            rotateKoordinates = xyz0
            Exit Function
        End If

        'Calculate radians from degrees since
        'the trigonometric functions use radians.
        radianer = CDec(rotation * (pi / 180D))

        Select Case axis
            Case CChar("x"), CChar("X")
                'Since we are rotating around the x-axis
                'the x-coordinate won't change.
                xyz1.x = xyz0.x

                'Calculate the length of the vector from origo to the coordinates given
                'NB: We only calculate the length in the yz-plane since we don't
                'do anything with the x-coordinate
                length = CDec(Sqrt(xyz0.y ^ 2D + xyz0.z ^ 2D))

                'IF y=0 we are on the z-axis, i.e: alfa0 = pi/2 eller alfa0=pi*3/2
                'If z=0 too won't be a problem
                If xyz0.y = 0 Then 'On the z-axis
                    alfa1 = CDec(IIf(xyz0.z > 0, (radianer + pi / 2D), (pi * (3D / 2D) + radianer)))
                Else
                    alfa1 = CDec(Atan(xyz0.z / xyz0.y) + radianer)
                End If
                xyz1.y = length * Cos(alfa1)
                xyz1.z = length * Sin(alfa1)
            Case CChar("y"), CChar("Y")
                xyz1.y = xyz0.y
                length = CDec(Sqrt(xyz0.x ^ 2D + xyz0.z ^ 2D))
                If xyz0.z = 0 Then ' On the x-axis
                    alfa1 = CDec(IIf(xyz0.x > 0, radianer + pi / 2D, pi * 3D / 2D + radianer))
                Else
                    alfa1 = CDec(Atan(xyz0.x / xyz0.z) + radianer)
                End If
                xyz1.z = length * Cos(alfa1)
                xyz1.x = length * Sin(alfa1)
            Case CChar("z"), CChar("Z")
                xyz1.z = xyz0.z
                length = CDec(Sqrt(xyz0.x ^ 2D + xyz0.y ^ 2D))
                If xyz0.x = 0 Then 'On the y-axis
                    alfa1 = CDec(IIf(xyz0.y > 0, radianer + pi / 2D, pi * 3D / 2D + radianer))
                Else
                    alfa1 = CDec(Atan(xyz0.y / xyz0.x) + radianer)
                End If
                xyz1.x = length * Cos(alfa1)
                xyz1.y = length * Sin(alfa1)
                'MsgBox(Sin(alfa1).ToString)
            Case Else
                Err.Clear()
                Err.Number = 5
                Err.Description = "You can only rotate around x, y or z -axis"
                Err.Raise(5)
                Exit Function
        End Select
        'Code below to ensure that I get exactly 0 when sin(alfa1) or cos(alfa1)
        'doesn't return 0 even thou alfa1 should be pi / 2 or pi / 4
        'If Abs(xyz1.x) < 10 ^ -12 Then xyz1.x = 0
        'If Abs(xyz1.y) < 10 ^ -12 Then xyz1.y = 0
        'If Abs(xyz1.z) < 10 ^ -12 Then xyz1.z = 0
        rotateKoordinates = xyz1
        Exit Function
    End Function

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TextBox1.Text = "z"
        TextBox2.Text = "90"
        TextBox3.Text = "0"
        TextBox4.Text = "3"
        TextBox5.Text = "0"
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim xyz0 As xyzType, xyz1 As xyzType
        xyz0.x = CDbl(TextBox3.Text.Trim)
        xyz0.y = CDbl(TextBox4.Text.Trim)
        xyz0.z = CDbl(TextBox5.Text.Trim)

        xyz1 = rotateKoordinates(CChar(TextBox1.Text.Trim), CDbl(TextBox2.Text.Trim), xyz0)
        TextBox6.Text = xyz1.x.ToString & ", " & xyz1.y.ToString & ", " & xyz1.z.ToString
    End Sub

End Class

                xyz1.x = length * Cos(alfa1)
                xyz1.y = length * Sin(alfa1)
            Case Else
                'Do exception stuff here
                Exit Function
        End Select
        return xyz1
      End Function

   xyz0.x = 0
   xyz0.y = 3
   xyz0.z = 0
   rotateKoordinates(CChar("z"), CDbl("90"), xyz0)

   length = CDec(Sqrt(xyz0.y ^ 2D + xyz0.z ^ 2D))