Tween Rotation / Shortest Distance?

[Ninjadoodle]

Hi @enpu / Panda People

Just wondering how I would go about tween the rotation of a sprite back to 0, by the shortest distance.

I'm pretty sure that right now, the tween always takes the same direction - even if its the longest way around.

[enpu]

@Ninjadoodle

What you want to do is to rotate your sprite to 0 or Math.PI * 2 (which is whole turn, 360 degrees), depending on which one is closest to the current rotation.

First you should convert your current rotation to value between 0 - Math.PI * 2. You can do that by using modulus operator

sprite.rotation = sprite.rotation % (Math.PI * 2);

Then just check if the rotation is more than Math.PI (which is half turn, 180 degrees). If it is, rotate to Math.PI * 2, if not then rotate to 0.

sprite.rotation = sprite.rotation % (Math.PI * 2);

var target = 0;
if (sprite.rotation > Math.PI) target = Math.PI * 2;

game.Tween.add(sprite, {
    rotation: target
}, 500).start();

 

[Ninjadoodle]

@enpu - Ahhh I get it so Math.PI * 2 is different than 0.

I was under the impression that when it reaches 360 degrees it resets to 0 again.

Thanks for this!!

[Ninjadoodle]

@enpu

I've noticed that when I rotate a sprite ...

this.playerShip.sprite.rotation += this.shipSpeed * Math.PI;

the rotation number keeps incrementing, instead of resetting.

So, two clockwise circles will be 720 degrees.

Do I have to reset manually?

[enpu]

@Ninjadoodle

You don't have to reset anything. That's why i first converted the rotation value in the example above, so no matter how high the value is

sprite.rotation = sprite.rotation % (Math.PI * 2);

After this, it will be between 0 - Math.PI * 2.

 

[Ninjadoodle]

@enpu - Nice, I understand now