Argh, _rotation help ><!

[ssjskipp]

Okay, so I made this little missile targeting AI:
Here
And as you can see [click to fire a missile], the missile automatically rotate to the new target. I Know why, but what I would like to know, is an efficent, non-laggy script that'll ease it into the rotation.

Any idea? [I've tried using the mx.tweens, some a > _rotation, etc. but rotation goes 0-360, so it makes it act weird...]

Here's my method of getting the rotation:
//Move the missile in the direction it's rotated to
_x += s*Math.sin((_rotation*Math.PI)/180);
_y -= s*Math.cos((_rotation*Math.PI)/180);
//Get rotation
x = this._x-my_target._x;
y = this._y-my_target._y;
a = -Math.atan2(x, y)/(Math.PI/180);
//Set Rotation
_rotation = a;

All of this is on the missile itself, and under onClipEvent(enterFrame){}
where my_target is the movieclip of it's current target.

Ideas?

[Pyromaniac]

instead of setting it to A, how about something like this?

if(_roation<a){
_roation++;
} else {
_rotation--;
}

[ssjskipp]

Tried it, rotations go from 0-360
so what that'll look like
say you're ay 0°
you have to rotate to 288°...
insed of going backwards like 50, you go clockwise about 288°, amknig it mess up, :o

[ssjskipp]

Bump!

[Go0gley]

Well first make sure rotation and a are 0-360....

_rotation += _rotation<0 ? 360 : (_rotation>=360 ? -360 : 0);
a += a<0 ? 360 : (a>=360 ? -360 : 0);

Then find the difference between the two angles, and make that 0-360 as well....

diff = a-_rotation;
diff += diff<0 ? 360 : (diff>=360 ? -360 : 0);

Now you know exactly how many degrees the missile has to turn to meet its target (without worrying about crossing from 359 degrees onto 0).

[ssjskipp]

...can Iget that translated into if then else, etc? I'm not good with the alternatve ways [? : etc.]

[Go0gley]

Haha... ok (if/else tends to run faster btw and I always use it when I'm not in a rush)

To make angle d between 0-360 degrees...

if (d<0) {
d+=360;
} else if (d>=360) {
d-=360;
}

That's assuming it never goes beyond -720 and 720 which it doesn't in ur situation

[ssjskipp]

wait, so now it's 0-360, but my problem still remains, jumping the 359-0 barrier ><

[Go0gley]

That's why instead of using the absolute rotation, we're gonna specify our own rotation (diff) relative to the rotation of the missile.

diff = a-_rotation;
if (diff<0) {
diff += 360;
} else if (diff>=360) {
diff -= 360;
}

So...

if (diff<=180) {
_rotation += turnspeed;
} else {
_rotation -= turnspeed;
}

Here's a graphic representation - http://www.pixfolder.com/images/4121.jpg - when _rotation = 60 and a = 300, the missile has to rotate anticlockwise (which crosses between 359 and 0 for _rotation but not for diff, so no problem)

If you're still having trouble understanding, I can give you one of my homing codes for you to figure out how they work.

[ssjskipp]

Ah, thanks :D! I get it now!

[Paranoia]

At 8/17/06 01:40 AM, ssjskipp wrote: wait, so now it's 0-360, but my problem still remains, jumping the 359-0 barrier ><

Actually, rotations like this are theoretically infinate (or looping), where 0º = 360º = 720º = 1080º and so on. So, giving something a rotation of 361º would be the same as giving it 1º.

And as best as I can remember, I believe rotations in Flash go from -180º to 180º. Those are, at least, the values I get from finding angles.