SpriteKit How to add laser beam and resize it at collision point - sprite

Question

I'm developing my first game with SpriteKit and I need to shoot a laser beam. I don't know how to do this since I don't know the size of the laser sprite, does it have to be with size of the screen height and crop the image when a collision is detected? can anyone point me to the right directions please? Have no idea about this XD
Thanks for your comments :D

Answer 1

This could be done by line-of-sight detection system described here in the section Searching for physics bodies :
Useful method would be enumerateBodiesAlongRayStart:end:usingBlock: from SKPhysicsWorld class which enumerates all the physics bodies in the scene that intersect a ray.
Basically you have to set start point and search for end point using the method above.When you know where is the intersection point(end point of laser beam) you can easily draw it.

Answer 2

This is a way late response, but I've got a really nice solution. Here's what it looks like (Swift 3):
In my code I'm calling this when I rotate the node I want the laser to shoot out of:
self.laser = SKShapeNode()
laser.lineWidth = 6
laser.glowWidth = 8
laser.strokeColor = .red
let _ = isTargetVisibleAtAngle(startPoint: startPoint, angle: selectedBeam!.zRotation + (CGFloat.pi / 2), distance: frame.size.height)
And this is the method. Obviously you put in whatever angle you want. The "foundOne" thing is so that it stops on the first object if that ray crosses through multiple targets
func isTargetVisibleAtAngle(startPoint: CGPoint, angle: CGFloat, distance: CGFloat) -> Bool {
let rayStart = startPoint
let rayEnd = CGPoint(x: rayStart.x + distance * cos(angle),
y: rayStart.y + distance * sin(angle))
let path = CGMutablePath()
path.move(to: rayStart)
path.addLine(to: rayEnd)
laser.path = path
var foundOne = false
let _ = physicsWorld.enumerateBodies(alongRayStart: rayStart, end: rayEnd) { (body, point, vector, stop) in
if !foundOne {
foundOne = true
let p = CGMutablePath()
p.move(to: rayStart)
p.addLine(to: point)
self.laser.path = p
}
}
return false
}