Direction between 2 Vectors

[Colin]

OK i have my camera system working exactly how i want it except for 1 problem, I have uploaded test build, press N to spawn a ball, then if you press down and to the left so the ball rolls around the camera will at 1 point spin in the opposite direction back to the ball.

New code:

//
// sets the look at target of the camera
//
procedure TCameraController.setTarget(const targ: TD3DXMatrix);
const
  tween = 0.01;
var
  pos, rV: TD3DXVector3;
  diff: TD3DXVector3;
begin
  pos := D3DXVector3(targ._41, targ._42+5, targ._43); // + 5 look slightly above the object

  D3DXVec3Subtract(diff, pos, position);
  D3DXVec3Normalize(diff, diff);

  rV := D3DXVector3(
            arctan2(diff.z, diff.x),
            arcsin(diff.y),
            0
          );


  rotation.x := (rV.x * tween) + rotation.x * (1 - tween);
  rotation.y := (rV.y * tween) + rotation.y * (1 - tween);
  rotation.z := (rV.z * tween) + rotation.z * (1 - tween);
end;

//
// sets the position of the camera somewhere behind the object, either facing or by velocity
//
procedure TCameraController.Follow(m: TD3DXMatrix; heading: TD3DXVector3);
const
  Dist = 20;
  MaxDist = 50;
  DefHeight = 15;
var
  tweenSpeed: TD3DXVector3;
  absdist: TD3DXVector3;

  pos: TD3DXVector3;
  gPoint: TD3DXVector3;
begin
  pos := D3DXVector3(m._41, m._42, m._43);

  if (heading.x > 0.00001) and (heading.z > 0.00001) then begin
    D3DXVec3Normalize(heading, heading);
    gPoint.x := m._41 + -Dist*heading.x;
    gPoint.z := m._43 + -Dist*heading.z;
    gPoint.y := m._42 + DefHeight;
  end else begin
    D3DXVec3Normalize(heading, pos);
    gPoint.x := m._41 + -Dist*heading.x;
    gPoint.z := m._43 + -Dist*heading.z;
    gPoint.y := m._42 + DefHeight;
  end;

  absdist := D3DXVector3(abs(pos.x-position.x),
            abs(pos.y-position.y),
            abs(pos.z-position.z)
          );

  if absdist.x > MaxDist then
    tweenSpeed.x := 0.005 * (absdist.x - (MaxDist-1))
  else
    tweenSpeed.x := 0.005;

  tweenSpeed.y := 0.005;

  if absdist.z > MaxDist then
    tweenSpeed.z := 0.005 * (absdist.z - (MaxDist-1))
  else
    tweenSpeed.z := 0.005;

  position.x := (gPoint.x * tweenSpeed.x) + position.x * (1 - tweenSpeed.x);
  position.y := (gPoint.y * tweenSpeed.y) + position.y * (1 - tweenSpeed.y);
  position.z := (gPoint.z * tweenSpeed.z) + position.z * (1 - tweenSpeed.z);
end;

else everything is nice, camera moves very smoothly for the most part, just this problem that is a pain...

Any ideas?

Thanks.