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[Solved] Attach a body without any influence on main body

Topics: Developer Forum
Oct 12, 2012 at 9:57 PM

Hi All,

I have a rather simple rectangular shape (some sort of a bullet) and I want to attach 2 circles to it. But when I go the box2d/farsser way using an instance of type body, a fixture and two joints the circles influence the flight path of the bullet. I want to attach the circles (eyes) to the bullet via the Body because it makes it a lot easier to always get the same position of the circles when the bullet rotates in the air. Basically the farseer physics engine calculates the position for me.

So how can I attach to a body another body that does not influence the physics of the first body?

Kind Regards

Oct 13, 2012 at 6:55 PM
Edited Oct 13, 2012 at 6:55 PM


You can make the eyes very light (lower density), they will have less influence on the bullet.

Or if you don't need they eyes to be simulated at all why don't you just apply some vector math to get where they are supposed to be without putting them in the world. Altenatively, using Farseer's helper methods, if in local coordinates to the bullet the eye is at (xeye,yeye) then doing bullet.GetWorldPoint(new Vector2(xeye,yeye)) will give you the eye coordinates after the bullet moves. Math is much faster than joints.

Oct 14, 2012 at 10:51 PM

Hi jerrysb,

thanks for your answer. I feared that doing the vector math is the correct way :-) I hoped that there is an easier way. Thanks again.