I'm trying to make an ARKit application where an SCNNode, in this case a box, is placed in front of the camera, facing the camera. As the user moves the camera around, objects are placed when a certain distance has been moved. This would leave you with a series of nodes facing the camera in a line, equally spaced.
I have this working to a certain extent, but my problem is with the rotation. I'm currently taking all axes of rotation, so as the user re-orients their phone, the rotation of the node matches. I want to restrict this to just the rotation around the y-axis. The ideal outcome is a domino-trail like look, with all the objects having the same x and z rotations, but potentially different y rotations.
I hope I've explained this clearly enough!
Here's the code I'm currently using:
func createNode(fromCameraTransform cameraTransform: matrix_float4x4) -> SCNNode {
let geometry = SCNBox(width: 0.02, height: 0.04, length: 0.01, chamferRadius: 0)
let physicsBody = SCNPhysicsBody(type: .dynamic, shape: SCNPhysicsShape(geometry: geometry))
physicsBody.mass = 1000
let node = SCNNode(geometry: geometry)
node.physicsBody = physicsBody
var translationMatrix = matrix_identity_float4x4
translationMatrix.columns.3.x = 0.05 // Moves the node down in world space
translationMatrix.columns.3.z = -0.1 // Moves the object away from the camera
node.simdTransform = simd_mul(cameraTransform, translationMatrix)
return node
}
I've tried different combinations of extracting values from the second column of the cameraTransform and setting them as eulerAngles, rotation and simdRotation, but to no avail.
I've also tried extracting values from the pointOfView of the current sceneView and assigning them to the same values as listed above, but again, no luck.
Any help would greatly appreciated!
I know a little bit about this, but am really just starting out with SceneKit and 3D transformations/matrices so be gentle with me!
I think I know what your trying to do, basically automatically drop each new domino so its evenly spaced following the camera.pointOfView trail.
You can update the new nodes euler angles y-axis to the same as the cameras pointofView eularAngles.y. So as you move the camera around the next node you are placing is always facing towards the camera (only rotating around the y-axis).
The renderer function updateAtTime below gets called everytime
the camera moves
func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
// You set the camera’s pointOfView’s eularAngle for y-xis to the node you are
about to place.
node.eulerAngles.y = (sceneView.pointOfView?.eulerAngles.y)!
I had this working in a playground so it does work.
Edit: This solution above angle was having a gimbal lock problem (as you went around in a circle in would reset its angle back to the axis.
So I found this approach using SCNBillboardConstraint works without experiencing the gimbal lock problem as you go around in circle.
let yFreeConstraint = SCNBillboardConstraint()
yFreeConstraint.freeAxes = .Y
node.constraints = [yFreeConstraint]
node.eulerAngles = node.presentation.eulerAngles
node.position = position
Related
I have this book, but I'm currently remixing the furniture app from the video tutorial that was free on AR/VR week.
I would like to have a 3D wall canvas aligned with the wall/vertical plane detected.
This is proving to be harder than I thought. Positioning isn't an issue. Much like the furniture placement app you can just get the column3 of the hittest.worldtransform and provide the new geometry this vector3 for position.
But I do not know what I have to do to get my 3D object rotated to face forward on the aligned detected plane. As I have a canvas object, the photo is on one side of the canvas. On placement, the photo is ALWAYS facing away.
I thought about applying a arbitrary rotation to the canvas to face forward but that then was only correct if I was looking north and place a canvas on a wall to my right.
I'v tried quite a few solutions on line all but one always use .existingPlaneUsingExtent. for vertical plane detections. This allows for you to get the ARPlaneAnchor from the
hittest.anchor? as ARPlaneAnchor.
If you try this when using .estimatedVerticalPlane the anchor? is nil
I also didn't continue down this route as my horizontal 3D objects started getting placed in the air. This maybe down to a control flow logic but I am ignoring it until the vertical canvas placement is working.
My current train of thought is to get the front vector of the canvas and rotate it towards the front facing vector of the vertical plane detected UIImage or the hittest point.
How would I get a forward vector from a 3D point. OR get the front vector from the grid image, that is a UIImage that is placed as an overlay when ARKit detects a vertical wall?
Here is an example. The canvas is showing the back of the canvas and is not parallel with the detected vertical plane that is the column. But there is a "Place Poster Here" grid which is what I want the canvas to align with and I'm able to see the photo.
Things I have tried.
using .estimatedVerticalPlane
ARKit estimatedVerticalPlane hit test get plane rotation
I don't know how to correctly apply this matrix and eular angle results from the SO answer.
my add picture function.
func addPicture(hitTestResult: ARHitTestResult) {
// I would like to convert estimate hitTest to a anchorpoint
// it is easier to rotate a node to a anchorpoint over calculating eularAngles
// we have all detected anchors in the _Renderer SCNNode. however there are
// Get the current furniture item, correct its position if necessary,
// and add it to the scene.
let picture = pictureSettings.currentPicturePiece()
//look for the vertical node geometry in verticalAnchors
if let hitPlaneAnchor = hitTestResult.anchor as? ARPlaneAnchor {
if let anchoredNode = verticalAnchors[hitPlaneAnchor]{
//code removed as a .estimatedVerticalPlane hittestResult doesn't get here
}
}else{
// Transform hitresult to world coords
let worldTransform = hitTestResult.worldTransform
let anchoredNodeOrientation = worldTransform.eulerAngles
picture.rotation.y =
-.pi * anchoredNodeOrientation.y
//set the transform matirs
let positionMatris = worldTransform.columns.3
let position = SCNVector3 (
positionMatris.x,
positionMatris.y,
positionMatris.z
)
picture.position = position + pictureSettings.currentPictureOffset();
}
//parented to rootNode of the scene
sceneView.scene.rootNode.addChildNode(picture)
}
Thanks for any help available.
Edited:
I have notice the 'handness' or the 3D model isn't correct/ is opposite?
Positive Z is pointing to the Left and Positive X is facing the camera for what I would expects is the front of the model. Is this a issue?
You should try to avoid adding node directly into the scene using world coordinates. Rather you should notify the ARSession of an area of interest by adding an ARAnchor then use the session callback to vend an SCNNode for the added anchor.
For example your hit test might look something like:
#objc func tapped(_ sender: UITapGestureRecognizer) {
let location = sender.location(in: sender.view)
guard let hitTestResult = sceneView.hitTest(location, types: [.existingPlaneUsingGeometry, .estimatedVerticalPlane]).first,
let planeAnchor = hitTestResult.anchor as? ARPlaneAnchor,
planeAnchor.alignment == .vertical else { return }
let anchor = ARAnchor(transform: hitTestResult.worldTransform)
sceneView.session.add(anchor: anchor)
}
Here a tap gesture recognized is used to detect taps within an ARSCNView. When a tap is detected a hit test is performed looking for existing and estimated planes. If the plane is vertical, we add an ARAnchor is added with the worldTransform of the hit test result, and we add that anchor to the ARSession. This will register that point as an area of interest for the ARSession, so we'll receive better tracking and less drift after our content is added there.
Next, we need to vend our SCNNode for the newly added ARAnchor. For example
func renderer(_ renderer: SCNSceneRenderer, nodeFor anchor: ARAnchor) -> SCNNode? {
if anchor is ARPlaneAnchor {
let anchorNode = SCNNode()
anchorNode.name = "anchor"
return anchorNode
} else {
let plane = SCNPlane(width: 0.67, height: 1.0)
plane.firstMaterial?.diffuse.contents = UIImage(named: "monaLisa")
let planeNode = SCNNode(geometry: plane)
planeNode.eulerAngles = SCNVector3(CGFloat.pi * -0.5, 0.0, 0.0)
let node = SCNNode()
node.addChildNode(planeNode)
return node
}
}
Here we're first checking if the anchor is an ARPlaneAnchor. If it is, we vend an empty node for debugging purposes. If it is not, then it is an anchor that was added as the result of a hit test. So we create a geometry and node for the most recent tap. Because it is a vertical plane and our content is lying flat need to rotate it about the x axis. So we adjust it's eulerAngles to have it be upright. If we were to return planeNode directly adjustment to eulerAngles would be removed so we add it as a child node of an empty node and return it.
Should result in something like the following.
I have a SCNNode - sceneNode - which is a child of rootNode and contains all of my child nodes. Upon the user tapping a button, I want to rotate the scene around a certain point on the y-axis. For example, the camera's point of view is known, and I want to rotate everything by 90º around the camera. The camera is no longer at 0, 0, 0.
I've tried playing around with the SCNMatrix4MakeTranslation function, and then changing the y value on the euler angles, but I've not been able to get it to work expectedly.
Your question is rather ambiguous, if you were to rotate the entire scene 90degrees “around the camera” the scene would end up next to the camera and you wouldn’t see it.
To rotate a SCNNode around a point other than its own pivot, as the question in the title, create a translation matrix that moves it to that point, multiply with a rotation matrix to the SCNNode, and then multiply with the inverse of the translation matrix.
However, what you probably want to do instead is do basically the same process with the camera node instead of the sceneNode. That will make the camera move around the sceneNode, giving the appearance the scene is rotating in place.
For example:
//get the current camera's transform and store it in cammat
GLKMatrix4 cammat = SCNMatrix4ToGLKMatrix4(self.myView.pointOfView.transform);
//create a rotation matrix of 90 degrees over axis Y
GLKQuaternion quaty = GLKQuaternionMakeWithAngleAndAxis(M_PI/2, 0, 1, 0);
GLKMatrix4 rotMat = GLKMatrix4MakeWithQuaternion(quaty);
//set the camera transform to rotMat * cammat, which basically rotates the camera first, and then moves it back to the same offset it was.
self.myView.pointOfView.transform = SCNMatrix4FromGLKMatrix4(GLKMatrix4Multiply(rotMat, cammat));
I’m using ARKit with SceneKit. When user presses a button I create an anchor and to the SCNNode corresponding to it I add a 3D object (loaded from a .scn file in the project).
The 3D object is placed facing the camera, with the same orientation the camera has. I would like to make it look like the object is laying on a plane surface and not inclined if it is that way. So, if I got it right, I’d need to apply a rotation transformation so that it’s rotation around the X and Z axis become 0.
My attempt at this is: take the node’s x and z eulerAngles, invert them, and rotate that amount around each axis
let rotationZ = rotationMatrixAroundZ(radians: -node.eulerAngles.z)
let rotationX = rotationMatrixAroundX(radians: -node.eulerAngles.x)
let rotationTransform = simd_mul(rotationTransformX, rotationTransformZ)
node.transform = SCNMatrix4(simd_mul(simd_float4x4(node.transform), rotationTransform))
This works all right for most cases, but in some the object is rotated in completely strange ways. Should I be setting the
rotation angle to anything else than just the inverse of the current Euler Angle? Setting the angles to 0 directly did not work at all.
I've come across this and figured out I was running into gimbal lock. The solution was to rotate the node around one axis, parent it to another SCNNode(), then rotate the parent around the other axis. Hope that helps.
You don't have to do the node transform on a matrix, you can simply rotate around a specific axis and that might be a bit simpler in terms of the logic of doing the rotation.
You could do something like:
node.runAction(SCNAction.rotateBy(x: x, y: y, z: z, duration: 0.0))
Not sure if this is the kind of thing you're looking for, but it is simpler than doing the rotation with the SCNMatrix4
Well, I managed a workaround, but I'm not truly happy with it, so I'll leave the question unanswered. Basically I define a threshold of 2 degrees and keep applying those rotations until both Euler Angles around X and Z are below the aforementioned threshold.
func layDownNode(_ node: SCNNode) {
let maxErrDegrees: Float = 2.0
let maxErrRadians = GLKMathDegreesToRadians(maxErrDegrees)
while (abs(node.eulerAngles.x) > maxErrRadians || abs(node.eulerAngles.z) > maxErrRadians) {
let rotationZ = -node.eulerAngles.z
let rotationX = -node.eulerAngles.x
let rotationTransformZ = rotationMatrixAroundZ(radians: rotationZ)
let rotationTransformX = rotationMatrixAroundX(radians: rotationX)
let rotationTransform = simd_mul(rotationTransformX, rotationTransformZ)
node.transform = SCNMatrix4(simd_mul(simd_float4x4(node.transform), rotationTransform))
}
}
I am trying to set up a simple scene (one spherical node and the default camera) in a square SceneView. Currently I set up the scene as below:
let scene = SCNScene()
let planet = SCNSphere(radius: 1.0)
let planetNode = SCNNode(geometry: planet)
scene.rootNode.addChildNode(planetNode)
To certain views, I also rotate the node as such:
let rotationNode = SCNNode()
rotationNode.addChildNode(planetNode)
scene.rootNode.addChildNode(rotationNode)
rotationNode.rotation = (SCNVector4: SCNVector4(x: 0, y: 0, z: 1, w: some_amount_of_radians))
What I noticed, however, is the objects that get rotated are smaller than the ones that don't get rotated. I am not really sure what the ratio is, but it seems to be dependent on how much rotation is added, to a point.
In the below screenshot, Earth is rotated 45 degrees, and the other 2 are not rotated. If I rotated it 90 degrees instead, there is no difference, which leads me to believe there is a square bounding box around the sphere and the default camera is forcing its point of view to contain this box.
I have also tried to change the euler angles, position, and scale of the rotated nodes to compensate, but no transormations I apply seem to have any effect. Any pointers for solving this camera issue would be perfect.
I am very new to SceneKit and your help will be really appreciated!
I have a 200x200 sized SCNView in my UIView, which is at the centre of super view.
I want to put a SCNCylinder inside, such that the SCNCylinder covers full SCNView. I read that all these views of Scenekit are defined in meters, so how do I form a relationship between the dimensions of my screen and the
SCNCylinder.
I tried:
var coinNode = SCNNode()
let coinGeometry = SCNCylinder(radius: 100, height: 2)
coinNode = SCNNode(geometry: coinGeometry)
coinNode.position = SCNVector3Make(0, 0, 0)
coinScene.rootNode.addChildNode(coinNode)
let rotate90AboutZ = SCNAction.rotateByX(-CGFloat(M_PI_2), y: 0.0, z: CGFloat(M_PI_2), duration: 0.0)
coinNode.runAction(rotate90AboutZ)
ibOutletScene.scene = coinScene
But this leaves a margin between my coinScene and the ibOutletScene. How do I remove this space?
I also tried adding Camera:
let cameraNode = SCNNode()
cameraNode.camera = SCNCamera()
cameraNode.position = SCNVector3Make(0, 0, 100)
coinScene.rootNode.addChildNode(cameraNode)
But I see random behaviour with this and the coinNode gets hidden! How should I position my camera? Or is there any other way to remove extra space from my ibOutletScene?
Edit:
This is how it looks if I don't add camera. There is a margin between red scene and green coin. I tried multiple sizes for the coin, but I am unable to remove this margin unless I add a camera. But, If I add camera, I get another problem, mentioned below this screenshot.
If I don't add the camera, The rotation animation on coin works perfectly, but If I add camera,the rotation enlarges the and then becomes small again with the animation. How can I rotate it on its axis, without increasing the size?
I am using following code to rotate the coin:
The same code works fine without camera, but enlarges the coin after adding camera. Checkout the snapshot.
let rotate = SCNAction.rotateByX(0, y: -2 * CGFloat(M_PI_2), z: 0, duration: 2)
coinNode.runAction(rotate)
The random behavior might be caused by the last line in your first code snippet. You're starting an animation, and then adding the scene to the view.
Instead, build your scene, attach it to the view, and then start your animation. Setting a non-zero duration for the action will give you a more pleasing transition.
As for the extra space, it would help us understand if you post a screenshot. But you're going to have to do a bit of trigonometry.
It looks like you have a scene that you want to be blocked by a coin, that then rotates out of the way? Simulate that yourself with real objects. Put your eye down at the edge of your desk. Put a coin out a ways from your eye. How far does that coin have to be in order to block particular objects farther away on your desk?
In SceneKit, you can query the field of view of the SCNCamera. You know the size of your coin and the size of the view. Calculate the distance from the camera needed for the projected diameter of your coin to equal the width of your view. Put the coin there.