Question by janla · May 09, 2013 at 05:48 PM · rigidbody force drag constraints

Drag around riggidbodies with a "pin"

Hi,

i'm currently working on a 2d pyhsics game and i wanted to know if it is possible to drag riggid bodies around via some kind of "pin" force?

There is a game called "little inferno" that has exaclty this kind of behavior: http://www.youtube.com/watch?feature=player_detailpage&v=04GSCt2Wiqo#t=117s

Right now i'm doing it with a simple transformation change, but obviously this doesn't lead to the desired result, since there's no real force applied. Ie. the object won't turn/dangle around the the point where i interact with it (if i grab a corner of it)

I've tired to make a drag behavior with forces, but it just led to completely unpredictible movements.

Then there is the other big problem of "pushing" objects through the walls. Right now i stop the dragging on collision with the walls, to avoid penetration, but if you move the objects really fast it doesn't trigger the the collision.

Do you guys think it's possible to solve this problems Unity at all? Or would i need to write my own engine (as they did in "little inferno")

PS: here is my test: http://www.gifery.com/experiments/unity/WebPlayer.html, if you like i can post my script too...

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robertbu · May 09, 2013 at 05:50 PM 0

You should be able to get something similar by using a joint. As a starting point, play with the standard DragRigidbody.js script. You can get it by selecting the 'Assets' menu and doing Import Package/Scripts.

janla · May 09, 2013 at 08:09 PM 0

Awesome, thank you very much! How did i miss that one???

janla · May 09, 2013 at 09:27 PM 0

This is even better concerning collisions: http://wiki.unity3d.com/index.php?title=DragObject

EDIT: but it won't "dangle"...

robertbu · May 09, 2013 at 09:35 PM 0

Thanks for the pointer. I did not know about this script.

Owen-Reynolds · May 10, 2013 at 07:19 AM 0

Adding forces does work, can look very pretty. Use AddForceAtPosition to pull from one edge. But, have to damp it way down when it is almost there, to avoid wiggling.