Fixed constraint removes 6 DOF (3 translation + 3 rotation). Welds two bodies together so they move as one rigid body.
inverse of initial relative orientation from body 1 to body 2
attachment point on body 1 in local space
attachment point on body 2 in local space
point constraint for translation (3 DOF)
rotation constraint (3 DOF) - keeps orientations locked
Fixed constraint removes 6 DOF (3 translation + 3 rotation). Welds two bodies together so they move as one rigid body.