Real-Time Physics Simulation Forum

Hi all,

Hoping all of you constraints experts can help me with this problem I'm having. Observe my preliminary, absolutely elementary rag-doll:


Nevermind that its shins are bending the wrong way--I'm not concerned with angular limits yet, but what I thought a ball and socket joint does is 2 things a) keeps 2 body parts together and b) limits rotation, gravity still does it's job and stuff--from what I thought. Well, here is what happens (first of all, I have rotated my character to a 45 degree angle and the first thing that happens should be it should become vertical (i'm holding the head up and letting the rest of the bodies fall). It doesn't do that. So I bring the body close to the ground and the shins bend as you can see, but when I lift it off the ground, they STAY bent. Something doesn't seem right. Anyone know what could be wrong? I'll keep chugging away at it but if you have any ideas please let me know, thanks.

Mike

So the answer turns out to be kinda embarassing. In GPG4, it shows you how to make a constraint for ball and socket, what it leaves out though is that it is for OBJECT coordinates (should be obvious though--I'm that dumb). Those that have used a block solver for normal impulse modeling will see the familiar jacobian vector cross product between a radius and a "normal" of some kind. Geesh.

Mike