ARKit - 获取从摄像机到锚点的距离

Question

我正在创建一个锚点并将其添加到相机前一定距离的ARSKView中，如下所示：

func displayToken(distance: Float) {
print("token dropped at: (distance)")
guard let sceneView = self.view as? ARSKView else {
return
}
// Create anchor using the camera's current position
if let currentFrame = sceneView.session.currentFrame {
// Create a transform with a translation of x meters in front of the camera
var translation = matrix_identity_float4x4
translation.columns.3.z = -distance
let transform = simd_mul(currentFrame.camera.transform, translation)
// Add a new anchor to the session
let anchor = ARAnchor(transform: transform)
sceneView.session.add(anchor: anchor)
}
}

然后为定位点创建节点，如下所示：

func view(_ view: ARSKView, nodeFor anchor: ARAnchor) -> SKNode? {
// Create and configure a node for the anchor added to the view's session.
if let image = tokenImage {
let texture = SKTexture(image: image)
let tokenImageNode = SKSpriteNode(texture: texture)
tokenImageNode.name = "token"
return tokenImageNode
} else {
return nil
}
}

这工作正常，我看到图像在适当的距离处添加。但是，我要做的是计算锚点/节点在您移动时在相机前的距离。问题是使用fabs(cameraZ - anchor.transform.columns.3.z(计算似乎立即关闭。请参阅下面的代码，该代码在update((方法中用于计算相机和对象之间的距离：

override func update(_ currentTime: TimeInterval) {
// Called before each frame is rendered
guard let sceneView = self.view as? ARSKView else {
return
}
if let currentFrame = sceneView.session.currentFrame {
let cameraZ =  currentFrame.camera.transform.columns.3.z
for anchor in currentFrame.anchors {
if let spriteNode = sceneView.node(for: anchor), spriteNode.name == "token", intersects(spriteNode) {
// token is within the camera view
//print("token is within camera view from update method")
print("DISTANCE BETWEEN CAMERA AND TOKEN: (fabs(cameraZ - anchor.transform.columns.3.z))")
print(cameraZ)
print(anchor.transform.columns.3.z)
}
}
}
}

感谢任何帮助，以便准确地获得相机和锚点之间的距离。

Answer 1

4x4 变换矩阵的最后一列是平移向量(或相对于父坐标空间的位置(，因此您只需减去这些向量即可获得两个变换之间的三维距离。

let anchorPosition = anchor.transforms.columns.3
let cameraPosition = camera.transform.columns.3
// here’s a line connecting the two points, which might be useful for other things
let cameraToAnchor = cameraPosition - anchorPosition
// and here’s just the scalar distance
let distance = length(cameraToAnchor)

您正在执行的操作无法正常工作，因为您正在减去每个向量的 z 坐标。如果两个点在 x、y 和 z 上不同，则仅减去 z 并不能获得距离。

Answer 2

这个是用于场景套件的，不过我会把它留在这里。

let end = node.presentation.worldPosition
let start = sceneView.pointOfView?.worldPosition
let dx = (end?.x)! - (start?.x)!
let dy = (end?.y)! - (start?.y)!
let dz = (end?.z)! - (start?.z)!
let distance = sqrt(pow(dx,2)+pow(dy,2)+pow(dz,2))

Answer 3

使用RealityKit，有一种稍微不同的方法可以做到这一点。如果您使用的是世界跟踪配置，则您的 AnchorEntity 对象符合HasAnchoring这将为您提供target。目标是AnchoringComponent.Target的枚举。它有一个案例.world(let transform).您可以将世界变换与摄像机的世界变换进行比较，如下所示：

if case let AnchoringComponent.Target.world(transform) = yourAnchorEntity.anchoring.target {
let theDistance = distance(transform.columns.3, frame.camera.transform.columns.3)
}

这花了我一点时间才弄清楚，但我认为其他可能正在使用 RealityKit 的人可能会从中受益。

Answer 4

正如@codeman上面提到的，这是正确的解决方案：

let distance = simd_distance(YOUR_NODE.simdTransform.columns.3, (sceneView.session.currentFrame?.camera.transform.columns.3)!);

Answer 5

3D 距离 - 您可以检查这些实用程序，

class ARSceneUtils {
/// return the distance between anchor and camera.
class func distanceBetween(anchor : ARAnchor,AndCamera camera: ARCamera) -> CGFloat {
let anchorPostion = SCNVector3Make(
anchor.transform.columns.3.x,
anchor.transform.columns.3.y,
anchor.transform.columns.3.z
)
let cametaPosition = SCNVector3Make(
camera.transform.columns.3.x,
camera.transform.columns.3.y,
camera.transform.columns.3.z
)
return CGFloat(self.calculateDistance(from: cametaPosition , to: anchorPostion))
}
/// return the distance between 2 vectors.
class func calculateDistance(from: SCNVector3, to: SCNVector3) -> Float {
let x = from.x - to.x
let y = from.y - to.y
let z = from.z - to.z
return sqrtf( (x * x) + (y * y) + (z * z))
}
}

现在您可以致电：

guard let camera = session.currentFrame?.camera else { return }
let anchor = // you anchor
let distanceAchorAndCamera = ARSceneUtils.distanceBetween(anchor: anchor, AndCamera: camera)