I want a node which I add to my scene to point north. I get the heading data from Core Location, so that represents the direction the device is currently facing at the point my scene was created (and thus the direction my root node faces), and then I add the heading to my new sceneNode's eulerAngles.y, to rotate it so it faces north.
func renderer(_ renderer: SCNSceneRenderer, didRenderScene scene: SCNScene, atTime time: TimeInterval) {
if sceneNode == nil,
let heading = self.locationManager.heading {
sceneNode = SCNNode()
sceneNode.eulerAngles.y += Float(heading).degreesToRadians
sceneView.scene.rootNode.addChildNode(sceneNode)
}
}
The heading information is correct, and so rotating it by that much does rotate it by the required amount, presuming that the heading is the same direction that my root node is facing. But I'm finding that my root node's direction is not equivalent to where the device's heading is, and can sometimes by wildly off. So that means the assumption that the heading is the same as the scene node's "heading" is incorrect, and I need to be able to know how far out from the heading it is, so I can then correct it properly within my sceneNode.
Change your session configuration's worldAlignment to .gravityAndHeading.
With the default .gravity alignment, there's no absolute reference for where the x and z axes of the AR world coordinate system point — their directions are based on the initial orientation of your device when the session starts.
With the .gravityAndHeading option, the x and z axes are aligned to compass directions, so you can safely orient content relative to compass directions.
Related
I'm trying to grasp the conversion thing in SpriteKit but despite having read the documentation and several posts on SO I can't seem to get it right. As far as I understand there are two coordinate systems that work independently of one another, one for the scene and one for the view, which is why I simply can't use the things like UIScreen.main.bounds.maxX to determine screen corners that the node can relate to. Am I getting this right?
Anyway, here's my attempt at converting coordinates:
let mySquare = SKShapeNode(rectOf: CGSize(width: 50, height: 50))
mySquare.fillColor = SKColor.blue
mySquare.lineWidth = 1
let myPoint = CGPoint(x: 200, y: 0)
let newPosition = mySquare.convert(myPoint, from: self)
mySquare.position = newPosition
print(newPosition)
self.addChild(mySquare)
The print returns the exact same position as went in so obviously I'm not doing this right, but I have tried a number of different constellations but with pretty much no result; the coordinates remain the same. I have also tried let myPoint = CGPoint(x: UIScreen.main.bounds.maxX, y: UIScreen.main.bounds.maxY) but same there; no conversion.
What am I missing? In my head I read the conversion above as "convert myPoint from the view coordinate system and use it for my node mySquare.
There are lots of coordinate systems floating around, and so lots of potential sources of confusion:
Scene coordinates: that's your game's world, and what you usually think about when imagining coordinates and how to position things overall.
Node: Nodes have their own coordinate system. Once you start building a hierarchy, that matters. Imagine, e.g., an on-screen joystick that has a background showing a graphic of movement directions and a central "knob" that the player can manipulate. You might represent the joystick as a node with two children. One child is a sprite for the background, and the other is a sprite for the knob. The background sprite would naturally be at position (0,0), meaning the center of the overall joystick. The knob would move around, with (0,0) meaning centered and maybe (0,100) meaning up a bit. The overall joystick might sit at (200,300) in the scene. Then the background sprite would show up at (200,300) in the scene and the knob, when up, would be at (200,300)+(0,100) = (200,400) in the scene. The convert(from:) and convert(to:) are for converting within the node hierarchy. You could ask where the knob is in the overall scene's coordinates by knob.convert(.zero, to: scene) or joystick.convert(knob.position, to: scene). You very rarely need to do that sort of conversion.
View coordinates: The view is a window on the scene, i.e., what's actually being shown. If you've got a full screen game, the view is basically determined by the screen size in points. How view coordinates map to scene coordinates determines what part of the scene you actually see. If you need to go between view coordinates and scene coordinates, you use the scene's convertPoint(fromView:) and convertPoint(toView:) methods.
If you don't do anything special and have the scene size the same as the view size, then the scene-view mapping will have (0,0) in the scene at the lower left corner of the view. Another common convention is to have (0,0) in the scene at the center of the screen by setting the scene's anchorPoint to (0.5,0.5). Or perhaps you've designed the scene so that the world is 2000x2000 in size and there will be a nontrivial scaling and possible letter-boxing or cropping involved (depending on the setting of the scene's scaleMode). Or if your game has a camera node and, e.g., the camera is set to follow the player around, then the view-to-scene mapping will be changing as the player moves.
In your code, calling mySquare.convert(from:) doesn't really even make sense since the square hasn't been added to the scene at the time you're doing the "conversion".
Anyway, if you really want to do something like "put a square in the top-left corner of the screen", then you can take the point in the view's frame and convert it to scene coordinates and set the square's position to that.
override func didMove(to view: SKView) {
...
mySquare.position = convertPoint(fromView: CGPoint(x: view.frame.minX, y: view.frame.minY))
addChild(mySquare)
...
}
Edit: I would encourage you though to think mostly in terms of the overall scene, after some initial consideration of how the game should map to devices with screens of different sizes and aspect ratios. Once you're thinking in terms of the scene, then the scene's frame (rather than the view's frame) becomes the most natural reference when you're imagining "at the left edge" or "near the bottom right".
I need to find the distance between two points inside a room using ARKit.
I will explain my scenario. Inside a room I have one predefined point. Say that point is (x1,y1,z1). I grabbed this value from ARKit ARCamera.transform's current position. I dynamically moved to another point whose ARCamera.transform's current position is (x2,y2,z2). My intention is to find real world distance between the two.
func session(_ session: ARSession, didUpdate frame: ARFrame) {
let currentFrame = frame.camera.transform
let x = frame.camera.transform.columns.3.x
let y = frame.camera.transform.columns.3.y
let z = frame.camera.transform.columns.3.z
print( "camera transform :\(x),\(y),\(z)")
}
Please find the above code which am using to get camera current poistion.
Now here is the problem. (x2,y2,z2) is diifferent on each time I test at the same physical point (Please note that my starting point is kept same, so ARKit session starts on the same point each time),so the distance varies largerly. In short I can't rely on ARKit to give my camera's current point in a usefull manner , ARCamera.transform's current position seems a random value which varies depends on some unknown facts.
On googling I have seen that ARCamera.transform's current position gives the position of device camera.
Can anybody point a solution or correct me if am wrong or please tell me what exactly is ARCamera.transform's current position or how can we use ARCamera.transform's current position in real world positioning?
Hey I'm trying to figure out. How to keep a simple node in place. As I walk around it in ARKit
Code:
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
if let planeAnchor = anchor as? ARPlaneAnchor {
if planeDetected == false { // Bool only allows 1 plane to be added
planeDetected = true
self.addPlane(node: node, anchor: planeAnchor)
}
}
}
This adds the SCNNode
func addPlane(node: SCNNode, anchor: ARPlaneAnchor) {
// We add the anchor plane here
let showDebugVisuals = Bool()
let plane = Plane(anchor, showDebugVisuals)
planes[anchor] = plane
node.addChildNode(plane)
// We add our custom SCNNode here
let scene = SCNScene(named: "art.scnassets/PlayerModel.scn")!
let Body = scene.rootNode.childNode(withName: "Body", recursively: true)!
Body.position = SCNVector3.positionFromTransform(anchor.transform)
Body.movabilityHint = .movable
wrapperNode.position = SCNVector3.positionFromTransform(anchor.transform)
wrapperNode.addChildNode(Body)
scnView.scene.rootNode.addChildNode(wrapperNode)
Ive tried adding a Plane/Anchor Node and putting the "Body" node in that but it still moves. I thought maybe it has something to do with the update function.
func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
}
Or most likely the position setting
wrapperNode.position = SCNVector3.positionFromTransform(anchor.transform)
Iv'e looked through every source / project file / video on the internet and nobody has a simple solution to this simple problem.
There are two kinds of "moving around" that could be happening here.
One is that ARKit is continuously refining its estimate of how the device's position in the real world maps to the abstract coordinate space you're placing virtual content in. For example, suppose you put a virtual object at (0, 0, -0.5), and then move your device to the left by exactly 10 cm. The virtual object will appear to be anchored in physical space only if ARKit tracks the move precisely. But visual-inertial odometry isn't an exact science, so it's possible that ARKit thinks you moved to the left by 10.5 cm — in that case, your virtual object will appear to "slip" to the right by 5 mm, even though its position in the ARKit/SceneKit coordinate space remains constant.
You can't really do much about this, other than hope Apple makes devices with better sensors, better cameras, or better CPUs/GPUs and improves the science of world tracking. (In the fullness of time, that's probably a safe bet, though that probably doesn't help with your current project.)
Since you're also dealing with plane detection, there's another wrinkle. ARKit is continuously refining its estimates of where a detected plane is. So, even though the real-world position of the plane isn't changing, its position in ARKit/SceneKit coordinate space is.
This kind of movement is generally a good thing — if you want your virtual object to appear anchored to the real-world surface, you want to be sure of where that surface is. You'll see some movement as plane detection gets more sure of the surface's position, but after a short time, you should see less "slip" as you move the camera around for plan-anchored virtual objects than those that are just floating in world space.
In your code, though, you're not taking advantage of plane detection to make your custom content (from "PlayerModel.scn") stick to the plane anchor:
wrapperNode.position = SCNVector3.positionFromTransform(anchor.transform)
wrapperNode.addChildNode(Body)
scnView.scene.rootNode.addChildNode(wrapperNode)
This code uses the initial position of the plane anchor to position wrapperNode in world space (because you're making it a child of the root node). If you instead make wrapperNode a child of the plane anchor's node (the one you received in renderer(_:didAdd:for:)), it'll stay attached to the plane as ARKit refines its estimate of the plane's position. You'll get a little bit more movement initially, but as plane detection "settles", your virtual object will "slip" less.
(When you make the node a child of the plane, you don't need to set its position — a position of zero means it's right where the plane is. Inf anything, you need to set its position only relative to the plane — i.e. how far above/below/along it.)
To keep an SCNNode in place you can disable sceneView plane detection once you get the result you desired.
let configuration = ARWorldTrackingConfiguration();
configuration.planeDetection = []
self.sceneView.session.run(configuration)
The reason for this is that ARKit constantly reestimates the position of the detected plane resulting in your SCNNode moving around.
So I have a bit of a project I am trying to do. I am trying to get the devices rotation relative to gravity, and translation from where it started. So basically getting "tracking" data for the device. I plan to basically apply this by making a 3d pt that will mimic the data I record from the device later on.
Anyway to attempt to achieve this I thought it would be best to work with scene kit that way I can see things in 3 dimensions just like the data I am trying to record. Right now I have been trying to get the ship to rotate so that it always looks like its following gravity (like its on the ground or something) no mater what the device rotation is. I figure once I have this down it will be a sinch to apply this to a point. So I made the following code:
if let attitude = motionManager.deviceMotion?.attitude {
print(attitude)
ship.eulerAngles.y = -Float(attitude.roll)
ship.eulerAngles.z = -Float(attitude.yaw)
ship.eulerAngles.x = -Float(attitude.pitch)
}
When you only run one of the rotation lines then everything is perfectly. It does behave properly on that axis. However when I do all three axis' at once it becomes chaotic and performs far from expected with jitter and everything.
I guess my question is:
Does anyone know how to fix my code above so that the ship properly stays "upright" no matter what the orientation.
J.Doe!
First there is a slight trick. If you want to use the iphone laying down as the default position you have to notice that the axis used on sceneKit are different then those used by the DeviceMotion. Check the axis:
(source: apple.com)
First thing you need to set is the camera position. When you start a SceneKit project it creates your camera in the position (0, 0, 15). There is a problem with that:
The values of eulerAngles = (0,0,0) would mean the object would be in the plane xz, but as long as you are looking from Z, you just see it from the side. For that to be equivalent to the iphone laying down, you would need to set the camera to look from above. So it would be like you were looking at it from the phone (like a camera, idk)
// create and add a camera to the scene
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
scene.rootNode.addChildNode(cameraNode)
// place the camera
cameraNode.position = SCNVector3(x: 0, y: 15, z: 0)
// but then you need to make the cameraNode face the ship (the origin of the axis), rotating it
cameraNode.eulerAngles.x = -Float(M_PI)*0.5 //or Float(M_PI)*1.5
With this we are going to see the ship from above, so the first part is done.
Now we gotta make the ship remain "still" (facing the ground) with the device rotation.
//First we need to use SCNRendererDelegate
class GameViewController : UIViewController SCNSceneRendererDelegate{
private let motion = CMMotionManager();
...
Then on viewDidLoad:
//important if you remove the sceneKit initial action from the ship.
//The scene would be static, and static scenes do not trigger the renderer update, setting the playing property to true forces that:
scnView.playing = true;
if(motion.deviceMotionAvailable){
motion.startDeviceMotionUpdates();
motion.deviceMotionUpdateInterval = 1.0/60.0;
}
Then we go to the update method
Look at the axis: the axis Y and Z are "switched" if you compare the sceneKit axis and the deviceMotion axis. Z is up on the phone, while is to the side on the scene, and Y is up on the scene, while to the side on the phone. So the pitch, roll and yaw, respectively associated to the X, Y and Z axis, will be applied as pitch, yaw and roll.
Notice I've put the roll value positive, that's because there is something else "switched". It's kinda hard to visualize. See the Y axis of device motion is correlated to the Z axis of the scene. Now imagine an object rotation along this axis, in the same direction (clock-wise for example), they would be going in opposite directions because of the disposition of the axis. (you can set the roll negative too see how it goes wrong)
func renderer(renderer: SCNSceneRenderer, updateAtTime time: NSTimeInterval) {
if let rot = motion.deviceMotion?.attitude{
print("\(rot.pitch) \(rot.roll) \(rot.yaw)")
ship.eulerAngles.x = -Float(rot.pitch);
ship.eulerAngles.y = -Float(rot.yaw);
ship.eulerAngles.z = Float(rot.roll);
}
Hope that helps! See ya!
I'm running some physics on a node. The node moves in all directions, but when tracking it's position it appears to be stationary.
func renderer(renderer: SCNSceneRenderer, didSimulatePhysicsAtTime time: NSTimeInterval) {
print("position.y: \(starNode.position.y)")
The message in the debugger is "position.y: 5.578" (which is the position I assigned in Scene Editor) for every call to renderer:didSimulatePhysicsAtTime method
What's going on?
that a look at the presentationNode property.