如何以绝对值获得 ARAnchor 的偏航、俯仰、滚动?

问题描述

这几天我一直在想办法解决这个问题.

I've been trying to figure this out for a few days now.

给定一个基于 ARKit 的应用程序，我可以在其中跟踪用户的面部，如何从锚点获得面部的绝对旋转?

Given an ARKit-based app where I track a user's face, how can I get the face's rotation in absolute terms, from its anchor?

我可以得到 ARAnchor 的变换，它是一个 simd_matrix4x4.有很多关于如何从矩阵中获取位置的信息(它是第 3 列)，但没有关于旋转的信息！

I can get the transform of the ARAnchor, which is a simd_matrix4x4.There's a lot of info on how to get the position out of that matrix (it's the 3rd column), but nothing on the rotation!

我希望能够通过传递 YAW、PITCH 和 ROLL 来控制应用程序外部的 3D 对象.

I want to be able to control a 3D object outside of the app, by passing YAW, PITCH and ROLL.

我最近尝试的东西实际上有点效果:

The latest I thing I tried actually works somewhat:

let arFrame = session.currentFrame!
guard let faceAnchor = arFrame.anchors[0] as? ARFaceAnchor else { return }

let faceMatrix = SCNMatrix4.init(faceAnchor.transform)
let node = SCNNode()

node.transform = faceMatrix
let rotation = node.worldOrientation

rotation.x .y 和 .z 有我可以使用的值，但是当我移动手机时，这些值会发生变化.例如，如果我转动 180 度并继续看手机，则值会根据手机的位置发生剧烈变化.

rotation.x .y and .z have values I could use, but as I move my phone the values change. For instance, if I turn 180˚ and keep looking at the phone, the values change wildly based on the position of the phone.

我尝试在 ARConfiguration 中更改世界对齐方式，但这并没有什么不同.

I tried changing the world alignment in the ARConfiguration, but that didn't make a difference.

我是否读错了参数?这应该容易得多！

Am I reading the wrong parameters? This should have been a lot easier!

推荐答案

我已经想通了...

一旦有了人脸锚点，就需要对其变换矩阵和相机的变换进行一些计算.

Once you have the face anchor, some calculations need to happen with its transform matrix, and the camera's transform.

像这样:

let arFrame = session.currentFrame!
guard let faceAnchor = arFrame.anchors[0] as? ARFaceAnchor else { return }

let projectionMatrix = arFrame.camera.projectionMatrix(for: .portrait, viewportSize: self.sceneView.bounds.size, zNear: 0.001, zFar: 1000)
let viewMatrix = arFrame.camera.viewMatrix(for: .portrait)

let projectionViewMatrix = simd_mul(projectionMatrix, viewMatrix)
let modelMatrix = faceAnchor.transform
let mvpMatrix = simd_mul(projectionViewMatrix, modelMatrix)

// This allows me to just get a .x .y .z rotation from the matrix, without having to do crazy calculations
let newFaceMatrix = SCNMatrix4.init(mvpMatrix)
let faceNode = SCNNode()
faceNode.transform = newFaceMatrix
let rotation = vector_float3(faceNode.worldOrientation.x, faceNode.worldOrientation.y, faceNode.worldOrientation.z)

rotation.x .y 和 .z 将返回面部的俯仰、偏航、滚动(分别)

rotation.x .y and .z will return the face's pitch, yaw, roll (respectively)

我添加了一个小的乘数并反转轴的 2，所以结果是这样的:

I'm adding a small multiplier and inverting 2 of the axis, so it ends up like this:

yaw = -rotation.y*3
pitch = -rotation.x*3
roll = rotation.z*1.5

呸！

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