Stopping at a point - vb.net

Question

I have a space ship that I want to turn to a destination angle. Currently it works like 90% of the time, but sometimes, it 'jumps' to the destination angle rather than moving smoothly. Here is my code:
a = System.Math.Sin(.destStoppingAngle + System.Math.PI)
b = System.Math.Cos(.destStoppingAngle + System.Math.PI)
c = System.Math.Sin(.msngFacing)
d = System.Math.Cos(.msngFacing)
det = a * d - b * c
If det > 0 Then
.msngFacing = .msngFacing - .ROTATION_RATE * TV.TimeElapsed
If det < 0.1 Then
.msngFacing = .destStoppingAngle
.turning = False
End If
Else
.msngFacing = .msngFacing + .ROTATION_RATE * TV.TimeElapsed
If det > 0.1 Then
.msngFacing = .destStoppingAngle
.turning = False
End If
End If

Answer 1

I would do it like this. First you need a function to lerp an angle (C code, port it yourself):
float lerpangle(float from, float to, float frac) {
float a;
if ( to - from > 180 ) {
to -= 360;
}
if ( to - from < -180 ) {
to += 360;
}
a = from + frac * (to - from);
return a;
}
Then, when starting the rotation you have the duration and stoppingangle as your own parameters. Get the startingangle from your object and startingtime (in something decently precise, milliseconds) and save them. The rotation then goes like this:
current_rotation = lerpangle(startingangle, stoppingangle,
(time.now - startingtime) / duration)