For my game I need to detect if nodes are still moving or not. Now I try to compare old and new positions within a time interval. If positions have the same value, nodes are not moving. And vice versa. Something like that:
if aStonesPositionsOld[index] == aStonesPositionsNew[index] {
print("# stone \(index) is not moving")
}
Does somebody know the better and easier way to check if node is moving or not?
Update. Answer to question of KnighOfDragon (How nodes begin moving?)
Nodes begin to move if being touched, or more exactly - moved with finger. Here is a code:
if touching {
let dt:CGFloat = 1.0/60.0
let distance = CGVector(dx: touchPoint.x-aCuesMe[touchingNr].position.x, dy: touchPoint.y-aCuesMe[touchingNr].position.y)
velocity = CGVector(dx: distance.dx/dt, dy: distance.dy/dt)
aCuesMe[touchingNr].physicsBody!.velocity=velocity
}
Since you are moving the object using the physics engine, all you have to do is check the velocity.
if let v = aCuesMe[someIndex].physicsBody?.velocity {
if v == CGVector(dx: 0, dy: 0) {
// Object has 0 velocity and is not moving
}
}
You can use GKAgent2D for this purpose from GameplayKit. It has property velocity. For more information read Apple's documentation: https://developer.apple.com/library/archive/documentation/General/Conceptual/GameplayKit_Guide/Agent.html#//apple_ref/doc/uid/TP40015172-CH8
and watch video:
https://developer.apple.com/videos/play/wwdc2016/608/
Related
I'm writing an application that displays chemical reactions and molecules in 3D. I read in all the values and positions of each atom from a text file and I am creating each atom shape with SCNSpheres. I have all the other values I need read in properly, but I can't figure out how to add keyframe animations to each node object in my scene.
I set up the molecules like this in ViewController.swift
func makeAtom(atomName: String, coords: [Double], scene: SCNScene) {
guard let radius = atomRadii[atomName]?.atomicRadius else { return }
atoms.append(Atom(name: atomName, x: coords[0], y: coords[1], z: coords[2], radius: radius, positions: []))
let atomGeometry = SCNSphere(radius: CGFloat(radius))
let atomNode = SCNNode(geometry: atomGeometry)
atomNode.position = SCNVector3(coords[0], coords[1], coords[2])
scene.rootNode.addChildNode(atomNode)
atomNodes.append(atomNode)
}
I know that the CAKeyframeAnimations are supposed to be set up like this
let animation = CAKeyframeAnimation()
animation.keyPath = "position.y"
animation.values = [0, 300, 0]
animation.keyTimes = [0, 0.5, 1]
animation.duration = 2
animation.isAdditive = true
vw.layer.add(animation, forKey: "move")
I just don't know where I should be declaring these animations and how the layers factor into all this. What layer should I be adding the animations to? And how can I trigger them to play? I've been searching all over the internet for help with this but I can't find anything that just shows a simple implementation.
I can provide more code if need be, I'm pretty new to StackOverflow and want to make sure I'm doing this right.
You can do it different ways, but I like this method: 58001288 (my answer here) as you can pre-build some animations using scenekit and then run them as a sequence.
Per the comment.. needed more room.
A sequence is a fixed thing. You can start, repeat, and stop it. However, it's hard to interact with it during phases.
If you really need to do that, then one way is to break up your sequence into its parts and call the next one yourself after a completion handler of the current one. I keep an array and a counter so that I know where I am. So basically it's just a queue of actions that I manage - if I'm on a certain step and the button is pressed, then I can cancel all current actions, set the desired effect, and restart it.
Edit:
The completion handler calls itself at the end of the function and advances its own array count so that the next one in the list can be called. This is obviously a bit dangerous, so I would use sparingly, but that's how I did it. I started mine on a timer, then don't forget to clean it up. I had a global GAME_ACTIVE switch and within the code I checked for it before calling myself again.
Edit2: This is actually a moveTo, but it's still just a custom set of SCNActions that calls itself when complete based on duration so that it immediately goes to the next one without a delay.
func moveTo()
{
let vPanelName = moves[moveCount]
let vLaneNode = grid.gridPanels[vPanelName]!.laneNodes[lane]
let vAction = SCNAction.move(to: vLaneNode.presentation.position, duration: TimeInterval(data.getAttackSpeed(vGameType: gameType)))
node.runAction(vAction, completionHandler:
{
self.moveCount += 1
if(self.moveCount >= self.moves.count - 1)
{
self.killMe(vRealKill: false)
return
}
else
{
self.moveTo()
}
})
}
EDIT: I have solved the problem and will post the solution in the next couple of days.
I'm building 3D achievements similar to Apple's Activity app.
I've already loaded my 3D model (a scene with a single node), can show it, and can tap on it to apply a rotational force:
#objc func objectTapped(_ gesture: UITapGestureRecognizer) {
let tapLocation = gesture.location(in: scnView)
let hitResults = scnView.hitTest(tapLocation, options: [:])
if let tappedNode = (hitResults.first { $0.node === badgeNode })?.node {
let pos = Float(tapLocation.x) - tappedNode.boundingBox.max.x
let tappedVector = SCNVector4(x: 0, y: pos, z: 0, w: 0.1)
tappedNode.physicsBody?.applyTorque(tappedVector,
asImpulse: true)
}
}
This works fine. Now to the tricky part:
I want the node to rotate until it either shows its front or backside (like in the Activity app), where it then should stop. It should stop naturally, which means it can overshoot a bit and then return.
To describe it with pictures - here I am holding the node in this position...
...and if I let go of the node, it will rotate to show the front side, which includes a little bit of overshooting. This is the ending position:
Since I'm quite new to SceneKit, I have troubles figuring out how to achieve this effect. It seems like I can achieve that by using SceneKit objects like gravity fields, without having to calculate a whole lot of stuff by myself, or at least that's what I'm hoping for.
I don't necessarily ask for a full solution, I basically just need a point in the right direction. Thanks in advance!
According to this article by apple Ray-Casting and Hit-Testing. I should use ray casting provided by RealityKit to detect the surfaces instead of hit testing provided by ARKit as apple says
but the hit-testing functions remain present for compatibility
. However,I can't find a way to know the extent of the surface detected by the raycast query.
So according to this code:
func startRayCasting() {
guard let raycastQuery = arView.makeRaycastQuery(from: arView.center,
allowing: .estimatedPlane,
alignment: .vertical) else {
return
}
guard let result = arView.session.raycast(raycastQuery).first else {
return
}
let transformation = Transform(matrix: result.worldTransform)
let plane = Plane(color: .green, transformation: transformation)
plane.transform = transformation
let raycastAnchor = AnchorEntity(raycastResult: result)
raycastAnchor.addChild(plane)
arView.scene.addAnchor(raycastAnchor)
}
I would expect that the plane I am creating would get the size and position of the plane detected. However this does not happen.
So my question is, Is ray casting suitable for detecting the surfaces size and location. Or its just for checking the 2d point location on a surface.
An Apple Documentation says here:
Raycast instance method performs a convex ray cast against all the geometry in the scene for a ray of a given origin, direction, and length.
and here:
Raycast instance method performs a convex ray cast against all the geometry in the scene for a ray between two end points.
In both cases raycast methods are used for detecting intersections. And in both cases these methods return an array of collision cast hit results.
That's all raycast was made for.
I was wondering if anyone would be able to offer me some help with using 3 nodes, I understand if I just have 2 nodes E.g. body A and body B but I'm struggling with adding a third body, I hoped it was as simple as body C but that wasn't the case.
This is the related code below:
struct CollisionCategoryBitmask {
static let Player: UInt32 = 0x00
static let Enemy1: UInt32 = 0x01
static let Enemy2: UInt32 = 0x02
}
func didBeginContact(contact: SKPhysicsContact) {
var updateHud = false
_ = (contact.bodyA.node != player) ? contact.bodyA.node : contact.bodyB.node
updateHud = slowDown(player)
}
This function below is intended to slow the player down when contacting Enemy1
func slowDown (player: SKNode) -> Bool {
player.physicsBody?.velocity = CGVector(dx: 0, dy: -50.0)
return true
}
and this below is intended to get the game to end when contacting Enemy2
func endGame (player: SKNode) -> Bool {
endOfGame()
return true
}
At the moment both functions work, but only one at a time, so when the player contacts either Enemy 1 or 2. I can currently either get the player to slow down or get the game to end by just changing the
updateHud = slowDown(player) line. So how can I adjust the code to have the two different outcomes happen when the player touches either Enemy 1 or 2.
Thanks
You are not understanding how didBeginContact works. Basically what is happening is when any 2 nodes make a contact, the first thing that the system will do is make sure that the category and contact bit masks line up to make a valid contact. If it does, then didBeginContact gets called. now inside this function, you have the 2 arbitrary nodes that made contact, called bodyA, and bodyB. What you need to do first, is figure out what bodyA and bodyB are. So the first thing you do, is check the categoryBitMask.
if(contact.bodyA.categoryBitMask == HERO) then contact.bodyA is a hero
Now that we know what categories these nodes refer to, we can then check what the node actually is. To do this, you can either check the name of the node
if(contact.bodyA.node.name == "Hero") then bodyA is the hero
Or compare the node itself
if(contact.bodyA.node == heroNode) then bodyA is the hero
Now do the same for bodyB.
You have established at this point what your nodes are, you can proceed with the outcome results that you need based on this information.
If Hero hits both enemy nodes at the same time, then you need to handle this as well. What is going to happen is 2 calls to didBeginContact will happen, you need to find a way to remember this, and do your contact code in either the didEvaluateActions, or didSimulatePhysicsMethod. I do not remember which of these follows didBeginContact, so you will have to test it out on your own.
I have been creating my own very simple test game based on Breakout while learning SpriteKit (using iOS Games by Tutorials by Ray Wenderlich et al.) to see if I can apply concepts that I have learned. I have decided to simplify my code by using an .sks file to create the sprite nodes and replacing my manual bounds checking and collision with physics bodies.
However, my ball keeps running parallel to walls/other rectangles (as in, simply sliding up and down them) any time it collides with them at a steep angle. Here is the relevant code--I have moved the physics body properties into code to make them more visible:
import SpriteKit
struct PhysicsCategory {
static let None: UInt32 = 0 // 0
static let Edge: UInt32 = 0b1 // 1
static let Paddle: UInt32 = 0b10 // 2
static let Ball: UInt32 = 0b100 // 4
}
var paddle: SKSpriteNode!
var ball: SKSpriteNode!
class GameScene: SKScene, SKPhysicsContactDelegate {
override func didMoveToView(view: SKView) {
physicsWorld.gravity = CGVector.zeroVector
let edge = SKNode()
edge.physicsBody = SKPhysicsBody(edgeLoopFromRect: frame)
edge.physicsBody!.usesPreciseCollisionDetection = true
edge.physicsBody!.categoryBitMask = PhysicsCategory.Edge
edge.physicsBody!.friction = 0
edge.physicsBody!.restitution = 1
edge.physicsBody!.angularDamping = 0
edge.physicsBody!.linearDamping = 0
edge.physicsBody!.dynamic = false
addChild(edge)
ball = childNodeWithName("ball") as SKSpriteNode
ball.physicsBody = SKPhysicsBody(rectangleOfSize: ball.size))
ball.physicsBody!.usesPreciseCollisionDetection = true
ball.physicsBody!.categoryBitMask = PhysicsCategory.Ball
ball.physicsBody!.collisionBitMask = PhysicsCategory.Edge | PhysicsCategory.Paddle
ball.physicsBody!.allowsRotation = false
ball.physicsBody!.friction = 0
ball.physicsBody!.restitution = 1
ball.physicsBody!.angularDamping = 0
ball.physicsBody!.linearDamping = 0
physicsWorld.contactDelegate = self
}
Forgot to mention this before, but I added a simple touchesBegan function to debug the bounces - it just adjusts the velocity to point the ball at the touch point:
override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
let touch = touches.anyObject() as UITouch
let moveToward = touch.locationInNode(self)
let targetVector = (moveToward - ball.position).normalized() * 300.0
ball.physicsBody!.velocity = CGVector(point: targetVector)
}
The normalized() function just reduces the ball/touch position delta to a unit vector, and there is an override of the minus operator that allows for CGPoint subtraction.
The ball/edge collisions should always reflect the ball at a precisely opposite angle but for some reason the ball really seems to have a thing for right angles. I can of course implement some workaround to reflect the ball's angle manually, but the point is that I want to do this all using the built in physics functionality in SpriteKit. Is there something obvious that I am missing?
This appears to be an issue with collision detection. Most have found solutions by using the didBeginContact and reapplying the force at an opposite direction. Note he says didMoveToView but corrects himself in a later comment to didBeginContact.
See comments at the bottom of the Ray Wenderlich tutorial here
I have a fix for the problem with the ball "riding the rail" if it
strikes at a shallow angle (#aziz76 and #colinf). I added another
category, "BorderCategory" and assigned it to the border PhysicsBody
we create in didMoveToView.
and a similar SO question here explaining why it is happening.
Even if you do that, though, many physics engines (including
SpriteKit's) have trouble with situations like this because of
floating point rounding errors. I've found that when I want a body to
keep a constant speed after a collision, it's best to force it to --
use a didEndContact: or didSimulatePhysics handler to reset the moving
body's velocity so it's going the same speed it was before the
collision (but in the opposite direction).
Also another thing I noticed is you are using a square instead of a circle for your ball and you may want to consider using...
ball.physicsBody = SKPhysicsBody(circleOfRadius: ball.size.width/2)
So turns out you aren't crazy which is always good to hear from someone else and hopefully this will help you find a solution that works best for your application.
I came up with a temporary solution that is working surprisingly well. Simply apply a very small impulse opposite of the border. You may need to change the strength based on the masses in your system.
func didBeginContact(contact: SKPhysicsContact) {
let otherNode = contact.bodyA.node == ball.sprite ? contact.bodyB.node : contact.bodyA.node
if let obstacle = otherNode as? Obstacle {
ball.onCollision(obstacle)
}
else if let border = otherNode as? SKSpriteNode {
assert(border.name == "border", "Bad assumption")
let strength = 1.0 * (ball.sprite.position.x < frame.width / 2 ? 1 : -1)
let body = ball.sprite.physicsBody!
body.applyImpulse(CGVector(dx: strength, dy: 0))
}
}
In reality, this should not be necessary, since as described in the question, frictionless, fully elastic collision dictates that the ball should rebound by inverting the x velocity (assuming side borders) no matter how small the collision angle is.
Instead, what is happening in the game is as if sprite kit ignores the X velocity if it is smaller than a certain value, making the ball slide against the wall without rebound.
Final Note
After reading this and this, it's obvious to me that the real answer is for any serious physics game you have, you should be using Box2D instead. You get way too many perks from the migration.
This problem only seems to occur when the velocity is small in either direction. However to reduce the effect it is possible to decrease the speed of the physicsWorld, e.g.,
physicsWorld.speed = 0.1
and then increase the velocity of the physicsBody, e.g.,
let targetVector = (moveToward - ball.position).normalized() * 300.0 * 10
ball.physicsBody!.velocity = CGVector(point: targetVector)
Add code below:
let border = SKPhysicsBody(edgeLoopFrom: self.frame)
border.friction = 0
border.restitution = 1
self.physicsBody = border
which will make your ball bounce back when it collides with wall.
Restitution is the bounciness of the physics body so setting it to 1 will bounce ball back.
I was seeing exactly the same issue, but the fix for me was not related to the collision detection issues mentioned in the other answers. Turns out I was setting the ball into motion by using an SKAction that repeats forever. I eventually discovered that this conflicts with SpriteKit's physics simulation leading to the node/ball travelling along the wall instead of bouncing off it.
I'm assuming that the repeating SKAction continues to be applied and overrides/conflicts with the physics simulation's auto-adjustment of the the ball's physicsBody.velocity property.
The fix for this was to set the ball into motion by setting the velocity on its physicsBody property. Once I'd done this the ball began bouncing correctly. I'm guessing that manipulating its position via physicsBody by using forces and impulses will also work given that they are a part of the physics simulation.
It took me an embarrassing amount of time to realise this issue, so I'm posting this here in case I can save anyone else some time. Thank you to 0x141e! Your comment put me (and my ball) on the right path.
The problem is twofold in that 1) it will not be solved by altering friction/restitution of the physics bodies and 2) will not be reliably addressed by a return impulse in the renderer() loop due to the contact occurring after the body has already begun decelerating.
Issue 1: Adjusting physics properties has no effect --
Because the angular component of the collision is below some predetermined threshold, the physics engine will not register it as a physical collision and therefore, the bodies will not react per the physics properties you've set. In this case, restitution will not be considered, regardless of the setting.
Issue 2: Applying an impulse force when the collision is detected will not produce consistent results -- This is due to the fact that in order to simulate restitution, one needs the velocity of the object just prior to impact.
-->For instance, if an object hits the floor at -10m/s and you want to simulate 0.8 restitution, you would want that object to be propelled 8m/s in the oppostie direction.
Unfortunately, due to the render loop, the velocity registered when the collision occurs is much lower since the object has already decelerated.
-->For example, in the simulations I was running, a ball hitting a floor at a low angle was arriving at -9m/s, but the velocity registered when the collision was detected was -2m/s.
This is important since in order to create a consistent representation of restitution, we must know the pre-collision velocity in order to arrive at our desired post-collision velocity...you can't ascertain this in the Swift collision callback delegate.
Solution:
Step 1. During the render cycle, record the velocity of the object.
//Prior to the extension define two variables:
var objectNode : SCNNode!
var objectVelocity : SCNVector3!
//Then, in the renderer delegate, capture the velocity of the object
extension GameViewController: SCNSceneRendererDelegate
{
func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval)
{
if objectNode != nil {
//Capture the object's velocity here, which will be saved prior to the collision
if objectNode.physicsBody != nil {
objectVelocity = objectNode.physicsBody!.velocity
}
}
}
}
Step 2: Apply a return impulse when the object collides, using the velocity saved prior to the collision. In this example, I am only using the y-component since I am simulating restitution in that axis.
extension GameViewController: SCNPhysicsContactDelegate {
func physicsWorld(_ world: SCNPhysicsWorld, didBegin contact: SCNPhysicsContact) {
let contactNode: SCNNode!
//Bounceback factor is in essence restitution. It is negative signifying the direction of the vector will be opposite the impact
let bounceBackFactor : Float! = -0.8
//This is the slowest impact registered before the restitution will no longer take place
let minYVelocity : Float! = -2.5
// This is the smallest return force that can be applied (optional)
let minBounceBack : Float! = 2.5
if contact.nodeA.name == "YourMovingObjectName" && contact.nodeB.name == "Border" {
//Using the velocity saved during the render loop
let yVel = objectVelocity.y
let vel = contact.nodeA.physicsBody?.velocity
let bounceBack : Float! = yVel * bounceBackFactor
if yVel < minYVelocity
{
// Here, the opposite force is applied (in the y axis in this example)
contact.nodeA.physicsBody?.velocity = SCNVector3(x: vel!.x, y: bounceBack, z: vel!.z)
}
}
if contact.nodeB.name == "YourMovingObjectName" && contact.nodeA.name == "Border" {
//Using the velocity saved during the render loop
let yVel = objectVelocity.y
let vel = contact.nodeB.physicsBody?.velocity
let bounceBack : Float! = yVel * bounceBackFactor
if yVel < minYVelocity
{
// Here, the opposite force is applied (in the y axis in this example)
contact.nodeB.physicsBody?.velocity = SCNVector3(x: vel!.x, y: bounceBack, z: vel!.z)
}
}
}
}