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Rotating around a point


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I need my space ship to follow the rotation of the planet it lands on. See example below:




My current approach is as follows:

ship.position.x = planet.x;ship.position.y = planet.y;ship.pivot.set(planet.width);ship.rotation = planet.rotation;

However, this results in the ship getting an incorrect position and rotation. See this (quite laggy) example.



Ideally, I would like to be able to write: 

ship.pivot.set(planet.position); // rotate around this global positionship.rotation = planet.rotation;

Any ideas?

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Just a thought: When your ship lands and the planet is already at lets say 45° and you just copy that then the ship will be set at 45° too.

It would make more sense if you increment the ships rotation by the same amount that you increment the planets rotation with.

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  • 2 weeks later...

I think the easiest way to do this would be to put the planet and the ship in a container (DIsplayObjectContainer) and then rotate the container.


I tried it, but couldn't get it working. Luckily, it turned out to be pretty easy to handle the rotation "manually". Here's the gist of it:

    var planet = shipEntity.misc.landedOnPlanet;    var rot = planet.position.rotation - shipEntity.misc.startRotation;    shipEntity.position.rotation = rot - Math.PI / 2;    shipEntity.position.x = planet.position.x - Math.cos(rot) * planet.sprite.radius * 1.2;    shipEntity.position.y = planet.position.y - Math.sin(rot) * planet.sprite.radius * 1.2;


shipEntity.misc.startRotation = entity.position.rotation - Math.atan2(planet.position.y - shipEntity.position.y, planet.position.x - shipEntity.position.x);

Here's another laggy video: http://recordit.co/I8QzIw

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