Swift 如何确定SKSPRITEKIT中SKSpriteNode的跳跃高度、与SKSpriteNode的碰撞

我使用applyImpluse进行固定跳跃，但它采用动态跳跃高度

   bird.physicsBody  =   SKPhysicsBody(circleOfRadius: bird.size.height / 2)
   bird.physicsBody?.dynamic   =   true
   bird.physicsBody?.friction              =   0.0
   bird.physicsBody?.restitution           =   0.0
   bird.physicsBody?.linearDamping         =   0.0
   bird.physicsBody?.affectedByGravity     =   true
   bird.physicsBody?.allowsRotation        =   false
   bird.physicsBody?.categoryBitMask       =   birdCategory
   bird.physicsBody?.contactTestBitMask    =   platformCategory 
   bird.physicsBody?.collisionBitMask      =   platformCategory 
   bird.physicsBody?.usesPreciseCollisionDetection = true
   bird.physicsBody?.applyImpulse(CGVectorMake(0, 15))

//我在用跟随跳跃

_bird.physicsBody?.applyImpulse(CGVectorMake(0,70.0))

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你是否也关闭了物理世界中的摩擦力？@Knight0fDragon bird.physicsBody？.friction=0.0我可以设置默认值吗？我也面临同样的问题。