Originally Posted by
RhinoBull
Aren't two points always connected by a straight line? So it could be 0, 180, 360...
That's right.
You'll need a third point (or vector) to get an angle.
This gives the bearing from one point on a flat 2D plane to another point, relative to the plane's 'north'.
vb Code:
Public Const Pi As Double = 3.14159265358979
Public Const Pi2 As Double = 3.14159265358979 * 2#
Public Const DegRad As Double = 3.14159265358979 / 180#
Public Const RadDeg As Double = 180# / 3.14159265358979
Public Function ATan2(ByVal X As Double, ByVal Y As Double) As Double
Dim sY As Double
Dim sX As Double
If Y < 0# Then sY = -Pi Else sY = Pi
If X = 0# Then
ATan2 = sY * 0.5
Else
If X < 0# Then sX = sY Else sX = 0#
ATan2 = Atn(Y / X) + sX
End If
' If ATan2 < 0 Then ATan2 = ATan2 + Pi2
End Function
X and Y are the relative dX and dY between both points.
The positive Y axis is north, the positive X axis is east.
The result is in radians.
Multiply by RadDeg to get the result in degrees.
(multiply by DegRad to do the opposite)
If you are working on the surface of a sphere or in 3D space then you'll need different methods.