我可以使用ARKit 2获取眼睛的测量值

Question

我正在开发一个项目，需要每只眼睛的大小和眼睛之间的距离使用ARKit和iPhone X上的真实深度相机和Xcode 10 beta 4上的iOS 12 beta 4。

由于我是ARKit的新手，我在网上搜索的解决方案很少。但是，我遇到了一个demo code on apple developer portal。在该代码中，我尝试获取所需的值。

@rickster的Also referred to the answer

我在ARSCNFaceGeometry和ARFaceAnchor上工作以获取少量值。

func update(withFaceAnchor anchor: ARFaceAnchor) {
    let faceGeometry = geometry as! ARSCNFaceGeometry
    faceGeometry.update(from: anchor.geometry)
    print("\nLook at Point :", anchor.lookAtPoint, "\nLeft :", anchor.leftEyeTransform, "\nRight :", anchor.rightEyeTransform)
}

输出：

看点：float3（0.14502259,0.2905016,0.97809345）

左：simd_float4x4（[[0.99312633，-0.030915117，-0.11289084,0.0）]，[0.0,0.9644885，-0.26412484,0.0）]，[0.11704737,0.26230934,0.9578589,0.0）]，[0.03311049,0.028666705,0.028539032,1.0） ]]）

右：simd_float4x4（[[0.9830616，-0.047965277，-0.17688738,0.0）]，[0.0,0.96514606，-0.26171172,0.0）]，[0.18327524,0.25727874,0.94879806,0.0）]，[ - 0.032072492,0.028482603,0.028181288,1.0 ）]]）

问题

1. 如何翻译这些值以使用它并获得一些坐标？
2. 这段代码能帮助我实现每只眼睛的大小和眼睛之间的距离。如果不是，那么我该怎么做才能进行测量？

Answer 1

在ARKit 2 / Xcode 10 beta 6 / iOS 12中，“lookAtPoint”无效;但是我能够得到“leftEyeTransform”和“rightEyeTransform”，然后可以使用这个代码计算眼间距离（在不同距离的两个人身上测试并用尺子验证！）：

func update(withFaceAnchor anchor: ARFaceAnchor) {
    let faceGeometry = occlusionNode.geometry as! ARSCNFaceGeometry
    faceGeometry.update(from: anchor.geometry)
    print("\nLook at Point:", anchor.lookAtPoint, "\nLeft:", anchor.leftEyeTransform, "\nRight:", anchor.rightEyeTransform)

var leftEyePosition = SCNVector3(anchor.leftEyeTransform.columns.3.x, anchor.leftEyeTransform.columns.3.y, anchor.leftEyeTransform.columns.3.z)
var rightEyePosition = SCNVector3(anchor.rightEyeTransform.columns.3.x, anchor.rightEyeTransform.columns.3.y, anchor.rightEyeTransform.columns.3.z)
let d = distance(float3(leftEyePosition), float3(rightEyePosition))
print("\nInter-eye distance in centimeters: ", d * 100)

}

一些示例输出：

Look at Point: float3(0.0, 0.0, 0.0) 
Left: simd_float4x4([[0.9997796, -0.0031222918, 0.020761598, 0.0)], [0.0, 0.98888004, 0.14871553, 0.0)], [-0.020995062, -0.14868274, 0.98866206, 0.0)], [0.031608228, 0.031428084, 0.026632207, 1.0)]]) 
Right: simd_float4x4([[0.99887705, 0.007054036, -0.04684897, 0.0)], [0.0, 0.9888536, 0.14889139, 0.0)], [0.047377057, -0.1487242, 0.98774314, 0.0)], [-0.031623494, 0.03171173, 0.02669965, 1.0)]])

Inter-eye distance in centimeters:  6.32324

注意：

Answer 2

你可以从变换中得到vector3：

var leftEyePosition = SCNVector3(leftTransform.columns.3.x, leftTransform.columns.3.y, leftTransform.columns.3.z)

var rightEyePosition = SCNVector3(rightTransform.columns.3.x, rightTransform.columns.3.y, rightTransform.columns.3.z)

然后你可以像这样得到2 SCNVector3的距离。

let d = distance(float3(leftEyePosition), float3(rightEyePosition)) 

结果将以米为单位，因此您可能希望将d除以100

Answer 3

没有简单的方法来实际获得学生自己的大小。有关更多信息，请参阅此StackOverFlow线程和Rickster提供的答案：Getting The Sizes Of The Eyes In ARKit

然而，使用leftEyeTransform和rightEyeTransforms可以获得眼睛之间的估计距离：

变换矩阵表示左右眼脸的位置和方向。

您感兴趣的是这些包含我们需要的数据的第3列。

计算距离的一种简单方法是使用不需要任何额外扩展的GLK助手。

这样的例子可能看起来像这样：

//----------------------
//MARK ARSCNViewDelegate
//----------------------

extension ViewController: ARSCNViewDelegate{

    /// Creates A GLKVector3 From a Simd_Float4
    ///
    /// - Parameter transform: simd_float4
    /// - Returns: GLKVector3
    func glkVector3FromARFaceAnchorTransform(_ transform: simd_float4) -> GLKVector3{

        return GLKVector3Make(transform.x, transform.y, transform.z)
    }

    func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {

        //1. Check We Have A Valid ARFaceAnchor
        guard let faceAnchor = anchor as? ARFaceAnchor else { return }


        //2. Get The Position Of The Left & Right Eyes
        let leftEyePosition = glkVector3FromARFaceAnchorTransform(faceAnchor.leftEyeTransform.columns.3)
        let righEyePosition = glkVector3FromARFaceAnchorTransform(faceAnchor.rightEyeTransform.columns.3)

        //3. Calculate The Distance Between Them
        let distanceBetweenEyesInMetres = GLKVector3Distance(leftEyePosition, righEyePosition)
        let distanceBetweenEyesInCM = distanceBetweenEyesInMetres/100
        print("The Distance Between The Eyes Is Approximatly \(distanceBetweenEyesInCM)")

    }

}

希望能帮助到你...

Answer 4

学生距离的一线解决方案：

simd_distance(faceAnchor.rightEyeTransform.columns.3, faceAnchor.leftEyeTransform.columns.3)

将其乘以100得到以厘米为单位的答案。如上所述，没有一种简单的方法可以测量虹膜或瞳孔的大小，因为您需要开发一种能够执行以下操作的算法：

1）找到圆圈并过滤描述虹膜的圆圈

2）使用ARKit计算像素到毫米的值并用它来计算虹膜大小