Shoot bullet in the Direction the Ship is Facing Swift and Sprite Kit

问题

I am making a space shooter game, and I would like the ship to be able to fire bullets in the direction it is facing. I have figured out how to make the bullet rotate in the direction of the ship, but I haven't gotten it to shoot in the right direction. At the moment, I only shoot up. I have a screen shot down below. How can I fix this? Here is my code:

if shootButton.containsPoint(location) {

            let Bullet = SKSpriteNode(imageNamed: "BulletGalaga.png")
            Bullet.zPosition = -5

            Bullet.position = CGPointMake(ship.position.x, ship.position.y)
            Bullet.zRotation = ship.zRotation
            Bullet.zPosition = ship.zPosition

            let action = SKAction.moveToY(self.size.height + 30, duration: 0.8)
            //let action = SKAction.moveTo(self.ship.size.height, duration: 0.8)
            let actionDone = SKAction.removeFromParent()
            Bullet.runAction(SKAction.sequence([action, actionDone]))

            Bullet.physicsBody = SKPhysicsBody(rectangleOfSize: Bullet.size)
            Bullet.physicsBody?.affectedByGravity = false
            Bullet.physicsBody?.dynamic = false
            self.addChild(Bullet)

        }

Thanks.

Screenshot

回答1:

You are setting the zPosition? you mean zRotation. and that will only calculate the angle that the bullet draws, you need to do some trig to figure out where the bullet will go to in a straight line:

PSEUDO CODE:

let action = SKAction.moveTo(
               CGPointMake(
                            travelDistance * cos(Bullet.zRotation) + Bullet.position.x,
                            travelDistance * sin(Bullet.zRotation) + Bullet.position.y
               ), 
               duration: 0.8)

回答2:

let action = SKAction.moveTo(
                CGPointMake(
                    400 * -cos(Bullet.zRotation - 1.57079633) + Bullet.position.x,
                    400 * -sin(Bullet.zRotation - 1.57079633) + Bullet.position.y
                ),
                duration: 0.8)

来源：https://stackoverflow.com/questions/35784784/shoot-bullet-in-the-direction-the-ship-is-facing-swift-and-sprite-kit

标签

ios

swift

sprite-kit

swift2