Direction between 2 Vectors

[Colin]

Dan, exactly the answer I needed, this is not the first time your post/replies have saved me from myself, I can't thank you enough but thank you very much

@User137, Thanks for your reply, your function will also be useful for other purposes. Thanks.

So my code so far (which works)

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

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

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

  D3DXVec3Lerp(rotation, rV, rotation, 0.1);
end;

my only problem now is using the DX function MatrixLookAt for matView seems to have a rotation limit on the yaxis.