'/==================================================================
'/ function rotatedKoordinates(axis as char, rotation as double, xyz as xyzType) as xyzType
'/ Returnerar (0, 0, 0) vid fel.
'/
'/ 20080509 Jens
'/ This function returns the new 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
'/ wieved from the positive end of the axis you rotate around.
'/ This function is for VB6 and it does need one Type to be declared:
'/ Public Type xyzType
'/   x As Double
'/   y As Double
'/   z As Double
'/ End Type
'/
'/ 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 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 xyz As xyzType) As xyzType
  Dim xyz0 As xyzType, xyz1 As xyzType
  Dim pi  As Double: pi = 3.14159265358979
  Dim radianer As Double, length As Double
  Dim alfa0 As Double, alfa1 As Double
  
  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 = rotation * pi / 180
  
  Select Case axis
  Case "x", "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 = Sqr(xyz0.y ^ 2 + xyz0.z ^ 2)
    
    '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 = IIf(xyz0.z > 0, radianer + pi / 2, pi * 3 / 2 + radianer)
    Else
      alfa1 = Atn(xyz0.z / xyz0.y) + radianer
    End If
    xyz1.y = length * Cos(alfa1)
    xyz1.z = length * Sin(alfa1)
  Case "y", "Y"
    xyz1.y = xyz0.y
    length = Sqr(xyz0.x ^ 2 + xyz0.z ^ 2)
    If xyz0.z = 0 Then ' On the x-axis
      alfa1 = IIf(xyz0.x > 0, radianer + pi / 2, pi * 3 / 2 + radianer)
    Else
      alfa1 = Atn(xyz0.x / xyz0.z) + radianer
    End If
    xyz1.z = length * Cos(alfa1)
    xyz1.x = length * Sin(alfa1)
Case "z", "Z"
    xyz1.z = xyz0.z
    length = Sqr(xyz0.x ^ 2 + xyz0.y ^ 2)
    If xyz0.x = 0 Then 'On the y-axis
      alfa1 = IIf(xyz0.y > 0, radianer + pi / 2, pi * 3 / 2 + radianer)
    Else
      alfa1 = Atn(xyz0.y / xyz0.x) + radianer
    End If
    xyz1.x = length * Cos(alfa1)
    xyz1.y = length * Sin(alfa1)
  Case Else
    Err.Clear
    Err.Number = 5
    Err.Description = "You can only rotate around x, y or z -axis"
    Err.Raise
    Exit Function
  End Select
  rotateKoordinates = xyz1
  Exit Function
End Function