static bool _KeepLength( ref Vector3 posTo, ref Vector3 posFrom, float keepLength )
{
Vector3 v = posTo - posFrom;
float len = SAFBIKVecLength( ref v );
if( len > IKEpsilon ) {
v = v * (keepLength / len);
posTo = posFrom + v;
return true;
}
return false;
}