I currently have two SKSpriteNodes on top of each other like so (The white part is one and the brown round circle part is the other one):
The white part is positioned 1/3 the way down on top of the round brown sprite node. In the picture, the brown round part has a SKPhysicsBody applied to it already as seen by the light blue outline around it. When I add a SKPhysicsBody around the top ovalish white part it pushes it up and not in the position I wanted it.
How can I have a SKPhysics body coving both bodies of sprites but not have the physics bodies push on one another which makes the white part move upwards? I would like the white part to stay in the position it was in the first image.
Thanks for anyone help!
Here's the code I used for the SKPhysicsBody's:
// create, position, scale & add the round body
roundBody = SKSpriteNode( imageNamed: "roundBody" )
roundBody.position = CGPoint( x: 207, y: 70 )
roundBody.zPosition = 1
roundBody.xScale = 0.3
roundBody.yScale = 0.3
// add sprite node to view
self.addChild( roundBody )
// create, position, scale & add the head
theHead!.position = CGPoint( x: 207, y: roundBody.frame.maxY / 1.15 )
theHead!.zPosition = 2
theHead!.xScale = 0.3
theHead!.yScale = 0.3
// setting up a SKPhysicsBody for the round body
roundBody.physicsBody = SKPhysicsBody( circleOfRadius: roundBody.size.width / 4 )
roundBody.physicsBody!.dynamic = true
roundBody.physicsBody!.affectedByGravity = true
roundBody.physicsBody!.allowsRotation = false
roundBody.physicsBody!.pinned = false
// setting up a SKPhysicsBody for the head
theHead!.physicsBody = SKPhysicsBody(circleOfRadius: theHead!.size.width / 2 )
theHead!.physicsBody!.dynamic = true
theHead!.physicsBody!.affectedByGravity = false
theHead!.physicsBody!.allowsRotation = false
theHead!.physicsBody!.pinned = false
I was able to figure out that if you use SKPhysicsJointPin it does the exact thing I needed! (Which was to basically pin a sprite head on it's body and share a physics body)
let joinTogether = SKPhysicsJointPin.jointWithBodyA(
roundBody.physicsBody!,
bodyB:theHead!.physicsBody!,
anchor: GPointMake(CGRectGetMidX(roundBody.frame),
CGRectGetMinY(theHead!.frame)))
scene!.physicsWorld.addJoint(joint)
Hope this helps someone in the future!
If you never want it to move, set it's .dynamic property to false. Then other objects may or may not bounce/collide with it (depending upon their collisionBitMask) but it won't move in response to those collisions.
Your own answer is correct and a better solution but just to explain further.
The reason of the bodies colliding is that by default a physics body's collision bit mask is set to all categories which means it will collide with everything. In your code you are not calling
roundBody.physicsBody?.collisionBitMask = ...
which is why its using the default values.
To change that you could give your body and head a different collisionBitMask.
Im sure you will deal with this sooner or later when you handle collisions
Also as a tip it's a better idea to not force unwrap the physics bodies unless you have too, even though you know they exist. So you should replace your ! with ? whenever possible.
Related
Edit: I have been able to solve this problem by using PhysicsEditor to make a polygonal physicsbody instead of using SKPhysicsBody(... alphaThreshold: ... )
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For some reason I'm having trouble with what I'm assuming is SKPhysicBodies being slightly off-place. While using showPhysics my stationary obstacle nodes appear to have their physicbodies in the correct position, however I am able to trigger collisions without actually touching the obstacle. If you look at the image below it shows where I have found the physicsbodies to be off centre, despite showPhysics telling me otherwise. (Note, the player node travels in the middle of these obstacle nodes).
I also thought it would be worth noting that while the player is travelling, its physicbody appears to travel slightly ahead but I figured this is probably normal.
I also use SKPhysicsBody(... alphaThreshold: ... ) to create the physicbodies from .png images.
Cheers.
Edit: Here's how I create the obstacle physicbodies. Once they're added into the worldNode they are left alone until they need to be removed. Apart from that I don't change them in any way.
let obstacleNode = SKSpriteNode(imageNamed: ... )
obstacleNode.position = CGPoint(x: ..., y: ...)
obstacleNode.name = "obstacle"
obstacleNode.physicsBody = SKPhysicsBody(texture: obstacleNode.texture!, alphaThreshold: 0.1, size: CGSize(width: obstacleNode.texture!.size().width, height: obstacleNode.texture!.size().height))
obstacleNode.physicsBody?.affectedByGravity = false
obstacleNode.physicsBody?.isDynamic = false
obstacleNode.physicsBody!.categoryBitMask = CC.wall.rawValue
obstacleNode.physicsBody!.collisionBitMask = CC.player.rawValue
obstacleNode.physicsBody!.contactTestBitMask = CC.player.rawValue
worldNode.addChild(obstacleNode)
The player node is treated the same way, here is how the player moves.
playerNode.physicsBody?.velocity = CGVector(dx: dx, dy: dy)
I'm assuming you aren't showing the exact images that you used to create your SKSpriteNode and SKPhysicsBody instances. Since you are using a texture to define the shape of your SKPhysicsBody you are likely running up against this:
SKPhysicsBody documentation
If you do not want to create your own shapes, you can use SpriteKit to create a shape for you based on the sprite’s texture.
This is easy and convenient but it can sometimes give unexpected results depending on the textures you are using for your sprite. Perhaps try making an explicit mask or using a simple shape to represent your physics body. There are very good examples and guidelines in that documentation.
I would also follow this pattern when you set the properties on your objects:
// safely unwrap and handle failure if it fails
guard let texture = obstacleNode.texture else { return }
// create the physics body
let physicsBody = SKPhysicsBody(texture: texture,
alphaThreshold: 0.1,
size: CGSize(width: texture.size().width,
height: texture.size().height))
// safely set its properties without the need to unwrap an Optional
physicsBody.affectedByGravity = false
// set the rest of the properties
// set the physics body property on the node
obstacleNode.physicsBody = physicsBody
By setting the properties on a concrete instance of SKPhysicsBody and fully unwrapping and testing Optionals you minimize the chances for a run-time crash that may be difficult to debug.
I have a SceneKit game in swift and in it I have a car with a dynamic physics body that is set up like this:
let carScene = SCNScene(named: "art.scnassets/truck.scn")!
let carNode = carScene.rootNode.childNode(withName: "Cube", recursively: true)!
let carPhysicsBody = SCNPhysicsBody(type: .dynamic,shape: SCNPhysicsShape(geometry: SCNBox(width: 5.343, height: 12.125, length: 4.373, chamferRadius: 0)))
carPhysicsBody.mass = 3
carPhysicsBody.friction = 2
carPhysicsBody.contactTestBitMask = 1
carNode.physicsBody = carPhysicsBody
carNode.position = SCNVector3(x: 0, y: 0, z: 5)
carNode.physicsBody?.applyForce(SCNVector3(x: 0, y: 50, z: 0), asImpulse: true)
car = carNode
floorScene.rootNode.addChildNode(car)
The floor's physics looks like this:
As you can see the car gets launched into the air. Then the gravity in the scene makes it fall, and instead of colliding with the floor, it goes right through it.
The gravity looks like this:
What should I change so it will collide with the floor?
I've made a sample macOS playground, available at github.com/heckj/scenekit-physics-playground that shows a physics body interacting. I suspect the core of the problem in your local example is that the floor object doesn't actually have an SCNPhysicsBody associated with it. Until I explicitly set it on SCNFloor (as static), the text blob "fell through" as you originally described.
I recommend adding sceneView.debugOptions = [.showPhysicsShapes] to see the relevant debugging shapes. I've made (and pushed) a few updates to the above repo. Using stock SCNFloor to establish geometry for the physics collection made a tiny target (which is why the slight horizontal impulse made it appear to "pass through"). This last update sets the floor geometry to a long, wide, thin box.
You want to set the floor to be of the type kinematic, not static. With the car being dynamic and the floor being static, the floor isn't interacting with other objects in any fashion, and you explicitly want a collision.
UPDATE: static vs. kinematic doesn't make a difference for the collision interaction, either work effectively the same way, but having a physics body, and verifying it's size or viewing the interaction with .showPhysicsShapes may answer the underlying question of why they're not interacting.
One of posible solutions for u is to set collisionMargin property for your car from 0.0 to probably 0.01, I had the same problem for ball and plane.
Hello I'm trying to spawn bullets at the bottom of my screen to travel upwards but the current code that I have spawns the bullets at the top of the screen. I've tried making the height negative and nothing happened. Here's the code I'm working with, thanks.
let randomBulletPosition = GKRandomDistribution(lowestValue: -300, highestValue: 300)
let position = CGFloat(randomBulletPosition.nextInt())
bullet.position = CGPoint(x: position, y: self.frame.size.height + bullet.size.height)
Some nice conversions will help you.
Now, do not do this all the time, this should be a one and done type deal, like in a lazy property.
First, we want to get the bottom of our view
let viewBottom = CGPoint(x:scene!.view!.midX,y:scene!.view!.frame.maxY) //In a UIView, 0,0 is the top left corner, so we look to bottom middle
Second, we want to convert the position to the scene
let sceneBottom = scene!.view!.convert(viewBottom, to:scene!)
Finally we want to convert to whatever node you need it to be a part of. (This is optional if you want to place it on the scene)
let nodeBottom = scene!.convert(sceneBottom,to:node)
Code should look like this:
let viewBottom = CGPoint(x:scene!.view!.midX,y:scene!.view!.frame.maxY)
let sceneBottom = scene!.view!.convert(viewBottom!, to:scene!)
let nodeBottom = scene!.convert(sceneBottom,to:node)
Of course, this is a little ugly.
Thankfully we have convertPoint and convert(_from:) to clean things up a little bit
let sceneBottom = scene.convertPoint(from:viewBottom)
Which means we can clean up the code to look like this:
let sceneBottom = scene.convertPoint(from:CGPoint(x:scene!.view!.midX,y:scene!.view!.frame.maxY))
let nodeBottom = node.convert(sceneBottom,from:scene!)
Then we can make it 1 line as:
let nodeBottom = node.convert(scene.convertPoint(from:CGPoint(x:scene!.view!.midX,y:scene!.view!.frame.maxY),from:scene!)
As long as the node is available to the class, we can make it lazy:
lazy var nodeBottom = self.node.convert(self.scene!.convertPoint(CGPoint(x:self.scene!.view!.midX,y:self.scene!.view!.frame.maxY),from:self.scene!)
This means the first time you call nodeBottom, it will do these calculations for you and store it into memory. Everytime after that, the number is preserved.
Now that you know where the bottom of the screen is in the coordinate system you want to use, you can assign the x value to whatever your random is producing, and you can subtract the (node.height * (1 - node.anchorPoint.y)) to fully hide your node from the scene.
Now keep in mind, if your node moves between various parents, this lazy will not update.
Also note, I unwrapped all optionals with !, you may want to be using ? and checking if it exists first.
Thanks in advance. I currently have a sprite controlled by the tilting of the device and would like every so often(NSTimer) for another sprite to appear behind it following it with the same physics. I have it set up, but i need the position to update every second so it follow behind it. How would I go about this? This is what I've tried/done.
let snakeBodyY = snakeHead.position.y - 5
let snakeBodyX = snakeHead.position.x - 5
snakeHead = SKSpriteNode(imageNamed: "snakeHead")
snakeHead.size = CGSize(width: 60, height: 60)
snakeHead.position = CGPoint(x: self.frame.midX, y: self.frame.midY - 50)
self.addChild(snakeHead)
snakeBody = SKSpriteNode(imageNamed: "snakeBody")
snakeBody.size = CGSize(width: 50, height: 50)
snakeBody.position.x = snakeBodyX
snakeBody.position.y = snakeBodyY
self.addChild(snakeBody)
Depends on how advance you need it,
if this is a free range 2D world you could assign the each new body to the tail so that the positions are relative to the snake, and always try to make the body parts move to the center of the previous body part up to the head.
Set up your sprite like this:
let snake = SKNode...
let head = SKSpriteNode...
let tail = SKSpriteNode...
//make sure you set up your positions for each body part, they should be relative to snake, not the screen
//setup collision so that tail and head can collide
head.physicsBody = SKPhysicsBody...
head.categoryBitMask = 1
head.collisionBitMask = 1
tail.physicsBody = SKPhysicsBody...
tail.categoryBitMask = 1
tail.collisionBitMask = 1
//setup restitution so that they do not bounce when colliding
head.restitution = 0
tail.restitution = 0
//add the parts to snake
snake.addChild(head)
snake.addChild(tail)
//Now you have a snake with a head and tail create an action to move the snake tail to the center of head
let moveToCenter = SKAction.moveTo(head.position, duration:0)
tail.runAction(moveToCenter)
//this will move the talk to try to get to the center of head, but collision physics will stop it from overlapping.
//Now everytime you want to add a new body
let body = SKSpriteNode...
body.physicsBody = SKPhysicsBody...
body.categoryBitMask = 1
body.collisionBitMask = 1
body.restitution = 0
snake.addChild(body)
let moveToCenter = SKAction.moveTo(tail.position, duration:0)
body.runAction(moveToCenter)
tail = body //lets make the tail the new piece to add
//Then on every update loop. you want to go through the children and do something like this
let previousChild = head
for child in snake.children
{
if child == head
{
continue;
}
child.removeAllActions()
let moveToCenter = SKAction.moveTo(previousChild.position, duration:0)
child.runAction(moveToCenter)
previousChild = child
}
Now if you find that this code may end up running slow for you, and don't mind a more stiff approach, you could also look up SKAction.followPath. Now I am not going to get into the details here, but basically what you need to do is record how your snake moves, then you generate a path with it, and use SKAction.followPath to make all the body parts move along the path.
If you are working in a 2d tiled world that only allows vertical and horizontal movement, you create an array of your sprites, and every time your snake makes a movement, you go down the snake and change its position to the previous body parts position
I am using Sprite Kit to add some circle icons to a scene. I have added some code to create a border around the outside of the scene size this is used to detect contact and remove the node from parent.
// Outside border collision detection
var largeBorder = CGRectMake(0, 0, size.width, size.height)
largeBorder.origin.x -= (mainIconRef.size.width + mainIconRef.size.width/3)
largeBorder.origin.y -= (mainIconRef.size.height + mainIconRef.size.height/3)
largeBorder.size.width += ((mainIconRef.size.width + mainIconRef.size.width/3) * 2)
largeBorder.size.height += ((mainIconRef.size.height + mainIconRef.size.height/3) * 2)
let pathMainView = CGPathCreateWithRect(largeBorder, nil)
self.physicsBody = SKPhysicsBody (edgeLoopFromPath: pathMainView)
self.physicsBody?.dynamic = false
self.physicsBody?.categoryBitMask = ColliderCategory.Wall.rawValue
self.physicsBody?.contactTestBitMask = ColliderCategory.Tap1.rawValue | ColliderCategory.Tap2.rawValue | ColliderCategory.Tap3.rawValue | ColliderCategory.TapFire.rawValue
self.physicsBody?.usesPreciseCollisionDetection = true
This is all working as expected. What I would like to do now is add another path/border/box in the middle of the screen and detect when the icons contact this. This is so I can tell they are at least a certain part of the size on the screen/scene itself.
What I am not sure about is that we set the self.physicsBody above. I do not want to override to it, I just want to add an additional border which is invisible (not shown) that I can track contact with (not collision). Is this possible without adding as a node?
Why not use an invisible node? Just turn off the physics for the node and pick the right shape for the physicsbody.
Set the right collisionbitmask, categorybitmask, contactbitmask etc and the icons will pass through the node and register "contact".
It'll do all of what you want.
Why don't you want to use a node?