How to show the bow string stretching animation (?)

Question

I was wondering how the animation in the angry birds of pulling the slingshot is done. One similar animation is available in this game but with a bow and arrow. I think both of them use the almost similar technique for it.

I tried to search for this on Google and all I got was the trajectory related stuff like calculating the trajectory of object once it is thrown. I could not find anything related to how the animation (?) for stretching the slingshot/bow string with respect to the force applied by user the bow string is achieved.

Can anybody point me in right direction in how to achieve that effect. Tutorials are welcome!

Answer 1

it's as simple as drawing a line from the anchor to the object after you calculate the location of it,

you can also make the string thinner as it gets stretched to imitate a rubber band stretching