I have a SpriteKit game in which balls bounce around, interacting with other objects.
One of those other objects is a spinner that should rotate around its center, but NOT change its x/y position. It should be stationary except for the rotation.
According to Apple's documentation, node.physicsBody.pinned = true should do exactly what I want, making it so that:
"the node’s position is fixed relative to its parent. The node’s position cannot be changed by actions or physics forces. The node can freely rotate around its position in response to collisions or other forces."
However, that's not what's happening. What's happening is that the spinner's y-axis position changes when a ball hits it squarely -- briefly moving down and then popping back into the correct position.
My code for the spinner (please assume all variables are defined):
for i in 0..<spinners.count {
let spinnerNode = SKSpriteNode(texture: texture)
spinnerNode.position = CGPoint(x: spinners[i].minX, y: spinners[i].minY)
spinnerNode.size = CGSize(width: spinners[i].width, height: spinners[i].height)
spinnerNode.physicsBody = SKPhysicsBody(texture: spinnerNode.texture!, size: CGSize(width: spinners[i].width, height: spinners[i].height))
spinnerNode.physicsBody?.isDynamic = true
spinnerNode.physicsBody?.affectedByGravity = false
spinnerNode.physicsBody?.pinned = true
addChild(spinnerNode)
}
Why on earth is my spinner node moving vertically when a ball collides with it? Why isn't .pinned working as advertised?
Thank you for your help!
I solved the problem by setting the spinner node's mass to a value slightly greater than that of the ball nodes.
node.physicsBody?.mass = 6.0
I have a sprite that the user is able to move side to side by pressing on the left or right side of the screen. If you hold down on either side, the player sprite will leave the screen. I want to stop that from happening using physic bodies, but I can't seem to make it work.
To start, here are my categories.
//Categories for physics bodies
let sceneCategory:UInt32 = 0x1 << 0 // Equal to 1
let playerCategory:UInt32 = 0x1 << 1 // Equal to 2
Here is where I set the physics body of the scene itself.
self.physicsWorld.contactDelegate = self
self.physicsBody = SKPhysicsBody(edgeLoopFrom: self.frame)
self.physicsBody?.categoryBitMask = sceneCategory
self.physicsBody?.contactTestBitMask = playerCategory
self.physicsBody?.collisionBitMask = 0
self.physicsBody?.isDynamic = false
This is how I have the physics set for the player itself. I'm trying to set the physics body around the car itself. Is the way I have it setup the same as setting an alpha mask physics body?
let texture = SKTexture(imageNamed: "PorscheBlue")
player.physicsBody = SKPhysicsBody(texture: texture, size: player.size)
player.physicsBody?.isDynamic = false
player.physicsBody?.categoryBitMask = playerCategory
player.physicsBody?.contactTestBitMask = sceneCategory
player.physicsBody?.collisionBitMask = 0
Then, in the didBegin method, I just wanted it to print showing that the method was called. This isn't happening though for some reason.
func didBegin(_ contact: SKPhysicsContact)
{
print("called")
}
Why isn't the didBegin method being called? Do I have the physics set up properly? How can I make it so the player isn't allowed to leave the screen when moving?
Thank you
EDIT: So when having the physics boundaries visible, it looks like the boundaries for the scene are only being drawn on the top and bottom. I can't see any lines being drawn on the sides. That may be the issue, but I can't get it to show on the sides.
I resolved my issue by changing the dynamic value. I had both set to false, which causes the didBegin function to not be called. At least one of the nodes needs to be dynamic.
I'm building a menu Game Scene where I have a Logo and 4 buttons, all of those have a SKPhysicsBody with the rectangle size of the image.
All of those I only set:
logo.physicsBody = SKPhysicsBody(rectangleOf: logo.size)
logo.physicsBody?.affectedByGravity = false
Full code of creating the objects (all are the same)
logo = SKSpriteNode(imageNamed: "logo")
logo.anchorPoint = CGPoint.zero
logo.name = "logo"
logo.zPosition = 2
logo.size = CGSize(width: 309, height: 272)
logo.setScale(Generic.utilities.getScale())
self.addChild(logo)
logo.position = CGPoint(x: self.frame.width/2 - logo.size.width/2, y: self.frame.height - logo.size.height - 40)
logo.physicsBody = SKPhysicsBody(rectangleOf: logo.size)
logo.physicsBody?.affectedByGravity = false
and during a button press I change all the nodes affectedByGravity to true so they can fall of the screen and new elements can come in.
The problem I'm having is that when I run the app, the elements are all shifted/tilted on the screen and not in their original position
All I wanted is for them to stay in their position until I click one of the buttons and then they can fall off the screen.
Any reason why when I set a physics body and affectedByGravity they all tilt like this?
Well, Thanks to #RonMyschuk and #Knight0fDragon I found out (didn't know before) that I could add to my Scene loading the following:
skView.showsPhysics = true
Which add border lines around the physicsBody of your nodes, that way you can see them interacting. And by doing that I saw that the physicsBody of one of my nodes was completely in a different position then it should
By taking care of this issue, everything went back to normal
I'm working on a new game and I faced a problem (making the edges of the screen act like walls !)
after some search I found this piece of code
self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
but the problem is that only the bottom and the top of the screen are working as edges while the right and the left edges aren't working (when I throw a ball to the left it goes for a while -of the screen- then hit the edge and return !)
Try this code:
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
and make sure you read over the SpriteKit Programming Guide (Listing 6-1 answers your question).
You have to subclass your GameScene with the SKPhysicsContactDelegate in order to have collisions exists in your Scene
class GameScene: SKScene, SKPhysicsContactDelegate {
physicsBody = SKPhysicsBody(edgeLoopFromRect: frame)
physicsWorld.contactDelegate = self
}
This question has already been asked and answered here: How to set contactDelegate for physicsWorld in SpriteKit?
Check "scaleMode" of your scene.
Seems it is "AspectFill" and part of your scene simply is out of view.
If so - please try "AspectFit" value.
Docs with explanation: https://developer.apple.com/reference/spritekit/skscenescalemode
I'm working in a side-scolling game and I need to know what nodes are in an area to implement something like "line of sight". Right now I'm trying using enumerateBodyiesInRect() however it's detecting bodies that are 20px or more from the evaluated rect and I cannot figure out why it's so imprecise.
This is what I'm trying now:
import SpriteKit
import CoreMotion
class GameScene: SKScene, SKPhysicsContactDelegate
{
var player = SKShapeNode()
var world = SKShapeNode()
var rShape = SKShapeNode()
override func didMoveToView(view: SKView) {
self.physicsWorld.contactDelegate = self
self.scaleMode = SKSceneScaleMode.AspectFit
self.size = view.bounds.size
// Add world
world = SKShapeNode(rectOfSize: view.bounds.size)
world.physicsBody = SKPhysicsBody(edgeLoopFromPath: world.path)
world.position = CGPointMake(self.frame.size.width/2, self.frame.size.height/2) // Move camera
self.addChild(world)
// Add player
player = SKShapeNode(rectOfSize: CGSize(width: 25, height: 25))
player.physicsBody = SKPhysicsBody(rectangleOfSize: player.frame.size)
player.physicsBody.dynamic = false
player.strokeColor = SKColor.blueColor()
player.fillColor = SKColor.blueColor()
player.position = CGPointMake(90, -50)
world.addChild(player)
}
override func update(currentTime: CFTimeInterval) {
// Define rect position and size (area that will be evaluated for bodies)
var r : CGRect = CGRect(x: 200, y: 200, width: 25, height: 25)
// Show rect for debug
rShape.removeFromParent()
rShape = SKShapeNode(rect: r)
rShape.strokeColor = SKColor.redColor()
self.addChild(rShape)
// Evaluate rect
rShape.fillColor = SKColor.clearColor()
self.physicsWorld.enumerateBodiesInRect(r) {
(body: SKPhysicsBody!, stop: UnsafePointer<ObjCBool>) in
self.rShape.fillColor = SKColor.redColor() // Paint the area blue if it detects a node
}
}
}
This code should show the evaluated rect and ray on the screen (for debugging purposes) and paint them red if they contact the player node. However you can see in the screenshot how it turns red when the player is 25px or more away from it, it's like if the drawing is a little bit off, or smaller than the actual area being evaluated. You can copy paste it to a project to duplicate the problem.
Could this be because this is just beta or am I doing something wrong?
You are creating a physical world where there is a specific rectangle that has 'special properties' - this is the rectangle that you use in enumerateBodiesInRect(). Why not create an invisible, inert physical body with the required rectangular dimension and then use SKPhysicsBody to check for collisions and/or contacts? You could then use allContactedBodies() or some delegate callbacks to learn what other bodies are inside your special rectangle.
Think of it like a 'tractor beam' or a 'warp rectangle'.
I believe you want SKPhysicsWorld's enumerateBodyiesInRect() instance method, which will iterate over all nodes in a given rectangle. If you're looking to get at the physics world through your scene, usage could look like this:
self.physicsWorld.enumerateBodiesInRect(CGRect(x: 0, y: 0, width: 50, height: 50)) {(body: SKPhysicsBody!, stop: UnsafePointer<ObjCBool>) in
// enumerates all nodes in given frame
}
I've experimented quite a bit with enumerateBodiesInRect now, and I've found it to be incredibly inaccurate. It seems to not have any of the claimed functionality, and instead produces random results. I honestly cannot even determine any pattern from its products.
enumerateBodiesAlongRay seems better, but still very buggy. The problem with that function seems to be the conversion between Screen and PhysicsWorld coordinates. I would avoid that one, as well.
I think your solution should simply be to use the existing contact detection system. All of your desired functionality can be written in the didBeginContact() and didEndContact() functions. This has the added benefit of allowing you to specify distinct functionality for both entering and leaving the area. You can also add particle effects, animations, and similar, as well as intentionally ignoring specific types of nodes.
The only thing to ensure success with this method is to clarify that the contact area has a unique category, that the contactTestBitMask contains all desired nodes and the collisionBitMask is set to 0.
The enumerateBodiesInRect method of SKPhysicsWorld expects the rect parameter to be in scene coordinates. This is important. If you have a scene hierarchy of nodes, you need to convert the rect you calculate from a reference node to the scene coordinates.
I faced a lot of issues with this method returning bodies that were off by values like 30px to the left etc. and finally realized the issue was because of the rect parameter not defined in scene coordinate space.
In my case, I had a worldNode inside my scene, and all objects were created in the worldNode. My camera was moving the worldNode about, and applying scaling to it for zooming out and in.
In order to use enumerateBodiesInRect correctly, I had to do something as follows:
// get your world rect based on game logic
let worldRect = getWorldRect()
// calculate the scene rect
let sceneRectOrigin = scene.convertPoint(worldRect.origin, fromNode:scene.worldNode)
let worldScale = scene.worldNode.xScale // assert this is not 0
// now to get the scene rect relative to the world rect, in scene coordinates
let sceneRect = CGRectMake( sceneRectOrigin.x, sceneRectOrigin.y, worldRect.width / worldScale, worldRect.height / worldScale)
world.physicsWorld.enumerateBodiesInRect(sceneRect) {
// your code here
}
Hope this helps.
I am not sure if this is a good practice. Correct me if not. But I am using
let shapeNode = SKShapeNode()
shapeNode.intersects(playerNode)
I checked selected nodes with simple loop if they intersect the player. Additionally I created SKShapeNodes which are drawn in front of nodes representing view sight of other actors in the game. They are moved along those actors.
There is only nodesAtPoint: method.
To achieve what you want you'd better to store all enemies in an array and have an int variable, something like nextEnemyIndex. This approach lets you to easily return the next enemy node, it's much more efficient than trying to find a node on the scene.
yes problem may occur because of your player's image, for example try to use 10px smaller body size:
player.physicsBody = SKPhysicsBody(rectangleOfSize: CGRectMake(self.frame.origin.x, self.frame.origin.y, self.size.width-10, self.size.height-10)));