Select which objects in the radial gravity field affect the speed
I'm working on an Xcode project with a bunch of swipes and sprites and I'm wondering how I can choose which objects are affected by ray gravity fields. I currently have two stars and some planets, and each star has a radial gravitational field following it. The problem is that stars are drawn to their own gravitational fields. How can I do this so that each gravity field affects only one star and all the planets, but not the next star. I know it has something to do with categoryBitMask and / or fieldBitMask, but I don't know exactly how to do it. Thank you in advance. Below is the code for the star and gravitational field. I don't want this gravitational field to affect this star.
class star: SKSpriteNode {
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
init(imageNamed: String){
let imageTexture = SKTexture(imageNamed: imageNamed)
super.init(texture: imageTexture, color: nil, size: imageTexture.size())
let radius = self.size.width / 2
self.physicsBody = SKPhysicsBody(circleOfRadius: radius )
physicsBody?.dynamic = false
}
}
let star1 = star(imageNamed: "star")
let gravityField1 = SKFieldNode.radialGravityField()
star1.position = CGPoint(x: self.size.width / 4, y: self.size.height / 2)
star1.physicsBody?.friction = 0
star1.physicsBody?.linearDamping = 0
star1.physicsBody?.angularDamping = 0
star1.physicsBody?.angularVelocity = 0.2
star1.zPosition = 1
star1.name = "star"
addChild(star1)
gravityField1.enabled = true;
gravityField1.position = CGPoint(x: self.size.width / 4, y: self.size.height / 2)
gravityField1.strength = Float(pow(radius1, 2)) * pow(10, -3)
addChild(gravityField1)
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Here is an example of how to set category and field discharge masks:
Specify Category Bit Masks for Gravity Fields
gravityField1.categoryBitMask = gravityField1Category
gravityField2.categoryBitMask = gravityField2Category
Set the bitmasks so that each star is affected by a different stellar gravity field, but not your own
star1.physicsBody?.fieldBitMask = gravityField2Category star2.physicsBody?.fieldBitMask = gravityField1Category
Set the bitmasks so that the planets are affected by both gravity fields
planet.physicsBody?.fieldBitMask = gravityField1Category | gravityField2Category
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