为何把精灵设置为刚体后原来设置的锚点改变了

Cocos2d-x
#1

pipeUp = Sprite::create(“pipe_up.png”);
pipeUp->setAnchorPoint(Point(0.5, 1)); //为何加没加这句没区别
PhysicsBody* pipeUpBody = PhysicsBody::createBox(pipeUp->getContentSize(),PHYSICSBODY_MATERIAL_DEFAULT);
pipeUpBody->setGravityEnable(false);
pipeUp->setPhysicsBody(pipeUpBody);

#2

源码里说 刚体的锚点位于（0.5,0.5），不可修改！