SKPhysicsJointSpring的damping和frequency属性有什么区别？我的代码是varspring=SKPhysicsJointSpring.jointWithBodyA(body1.physicsBody,bodyB:body2.physicsBody,anchorA:body1.position,anchorB:body2.position)spring.frequency=1.8spring.damping=0.5self.physicsWorld.addJoint(spring1)body1.physicsBody?.dynamic=falsebody2.