Joint Creation

[Eric]

If I create a Ball joint between two Bodies, The first body is a box with mass 1 sitting on the "Ground" I have another body that is moving past it and above it.

 

When I create the joint how is it oriented in relation to the two Bodies? I assume the ends are at the parent and child but the Position of the "Pin" If I use Vec3(0,-1,0) Where does the pin get created? Is it local to the parent? I can't seem to get these things to work.

 

Basically, I want the Child to kind of dangle below the Parent, allowed to swing .

 

I hope I made sense.

 

Any insight would be greatly appreciated.

 

Thanks,

Eric

[Canardia]

1) A joint is always created at a absolute global position. For example, if your body is at 0,0,10, then you must create the joint also at 0,0,10, if you want the joint to be at the center of the body.

 

2) The pin of a joint is not a position, but a direction vector. If your ball A is a position 0,0,0, and ball B is a at positon 0,0,1, then you create a ball joint from ballA to ballB at position 0,0,0 with pin 0,0,1. It's usually good to use normalized vectors for the pin, so Length(pin)==1.

[Josh]

The position of a joint is the point where it rotates around. If you want the child joint to swing around the parent, the joint position should be the same as the parent's global position.