It seems the defaults are for some springyness, but I don't want my joints to be springy at all. How can this be achieved? The setSpring() method isn't very well documented. I tried setting the values to very positive infinity, negative infinity, and zero, but none of them seem to be right. I've got a game set up with a PhysicsPicker active, and i still am able to pull the joints apart (although they go back when I release the mouse)… this is what I'm trying to prevent. Thanks!
The reason that they go back when you release the mouse is because the simulation is trying to restore the joint to its "jointed" position. Now, if it bounces back and forth, back and forth, … when you release it, then it is obviously acting like a spring. If it just returns to its position, then that is expected behavior for joints.
The physics picker uses joints as well. The simulation tries to satisfy the constraints for all joints but it can't if you pull your joints apart. Generally physics simulation is only an approximation. Springiness should be off when you specify NaN (the default).