is this impossible?

[ihoss.com]

I have been messing about with this for some time now, and I can't get it to work. The effect I want is an mc that rotates to point towards a point on the stage. This is easy using Math.atan2 like this:

	xd = _root._xmouse-_x;
	yd = _root._ymouse-_y;
	_rotation= Math.atan2(yd, xd)/toRad;

The effect I want is for the mc to rotate slowly (at constant speed) towards that point, taking the shortest route. You might think this is easy, but when the mc (mouse in this case) is in a certain direction the mc rotates the longer way towards it, instead of the shortest.

Has anyone got code that can make the effect? I'm almost giving up.

[tonypa]

Try the idea Arne The Turtle posted in the end of this thread:
http://www.flashkit.com/board/showthread.php?t=509004

[ihoss.com]

Well, that doesen't work either. It will rotate right when the mouse is below, to the right and to the left, but when you move it up it doesen't work.

[Gloo pot]

Im only new at flash but im gona give it ago, i also wanted to do this

[Gloo pot]

Im sorry but tony's example was correct and i got it working like this.
Create an MC stick in on da stage give it a instance called mc1 and stick this code on the main timeline. It will rotate towards the mouse traverling the shortests possable distance. Its quite nice realy.

onEnterFrame = function () {
	var rotation_speed = 10;
	var xd = mc1._x-_xmouse;
	var yd = mc1._y-_ymouse;
	var an = Math.atan2(yd, xd);
	var an = an*180/Math.PI;
	if (mc1._rotation>an) {
		if (mc1._rotation-an<=180) {
			mc1._rotation -= rotation_speed;
		} else {
			mc1._rotation += rotation_speed;
		}
	} else if (mc1._rotation != an) {
		if (an-mc1._rotation<=180) {
			mc1._rotation += rotation_speed;
		} else {
			mc1._rotation -= rotation_speed;
		}
	}
};

There was only one problem with that, when it had aligned it self with the target (the mouse in this case) you get some jerking because it cant go dircelty %100 in that direction.

Thanks tony for that link.

[tonypa]

Well, it was quite old thread so I decided to write new code based on vectors:

//declare mc
mcname=_root.mc;
//reset angle
mcname.angle=0;
//rotation speed
mcname.rotSpeed=2;
//set function to enterframe event
mcname.onEnterFrame=rotate;
function rotate(){
	this._rotation=this.angle;
	var rAng=this.angle/180*Math.PI;
	//find current vector
	var vx1=Math.cos(rAng);
	var vy1=Math.sin(rAng);
	//find vector to mouse coordinates
	var vx2=this._x-_root._xmouse;
	var vy2=this._y-_root._ymouse;
	var dist=Math.sqrt(vx2*vx2+vy2*vy2);
	//normalise
	vx2=vx2/dist;
	vy2=vy2/dist;
	//find dot product between left normal and vector to mouse
	var dp = vy1*vx2 - vx1*vy2;
	if(dp<-this.rotSpeed/90){
		//rotate counter-clockwise
		this.angle-=this.rotSpeed;
	}else if(dp>this.rotSpeed/90){
		//rotate clockwise
		this.angle+=this.rotSpeed;
	}
}

this.rotSpeed/90 is to avoid jerking, I dont have theory for that value, but this looked about right.

The code uses dot product of 2 vectors which show how both vectors are directed.

[ihoss.com]

if (_rotation<0) {
_rotation = 359;
}
if (_rotation>359) {
_rotation = 0;
}
was causing the problem. Don't know why it is there.

The vector one works perfectly

Thanks alot!

[artlink]

if (MCNAME._rotation<0) {
(MCNAME._rotation = 359;
}
if ((MCNAME._rotation>359) {
(MCNAME._rotation = 0;
}

[ihoss.com]

yeah, I know that, but I didn't do it from root, so I don't need the mc name there

[Gloo pot]

Hey tony thats some nice code there, and it was preaty simple to follow as well.