将ARFaceAnchor从左手坐标系切换到右手坐标系 [英] Flip ARFaceAnchor from left-handed to right-handed coordinate system
问题描述
在通过打印faceAnchor.transform.columns.3进行一些测试之后，在SO中进行挖掘: ARFaceAnchor有负Z位置?和Apple文档: ARFaceAnchor ，我意识到z轴实际上是翻转的，并且不是文档中的右手坐标系. ARFaceAnchor声明坐标:
After some testings by printing faceAnchor.transform.columns.3, digging in SO: ARFaceAnchor have negative Z position? and Apple's documentation: ARFaceAnchor, I realized that the z axis is actually flipped and it is not the right-handed coordinate system as in the documentation. The ARFaceAnchor claims the coordinate:
x的正方向指向观看者的右侧(即脸部自己的左手)，y的正方向指向上(相对于脸部本身，而不是世界)，z的正方向则指向观看者的外侧.面对(面向观众)
the positive x direction points to the viewer’s right (that is, the face’s own left), the positive y direction points up (relative to the face itself, not to the world), and the positive z direction points outward from the face (toward the viewer)
萨拉斯瓦蒂(Sarasvati)对进行改造提出了建议:
Sarasvati has given a suggestion on doing the transformation:
func faceAnchorPoseToRHS(_ mat: float4x4) -> float4x4 {
let correctedPos = float4(x: mat.columns.3.x, y: mat.columns.3.y, z: -mat.columns.3.z, w: 1)
let quat = simd_quatf(mat)
let newQuat = simd_quatf(angle: -quat.angle, axis: float3(quat.axis.x, quat.axis.y, -quat.axis.z))
var newPose = float4x4(newQuat)
newPose.columns.3 = correctedPos
return newPose
}
基于Andy Fedoroff的更新:
Updates based on Andy Fedoroff:
extension ViewController: ARSCNViewDelegate {
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
guard let faceAnchor = anchor as? ARFaceAnchor else { return }
currentFaceAnchor = faceAnchor
if node.childNodes.isEmpty, let contentNode = selectedContentController.renderer(renderer, nodeFor: faceAnchor) {
node.addChildNode(contentNode)
}
selectedContentController.session = sceneView?.session
selectedContentController.sceneView = sceneView
}
/// - Tag: ARFaceGeometryUpdate
func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
guard anchor == currentFaceAnchor,
let contentNode = selectedContentController.contentNode,
contentNode.parent == node
else { return }
sceneView.session.currentFrame!.anchors.first!.transform
print(currentFaceAnchor!.transform.columns.3)
selectedContentController.session = sceneView?.session
selectedContentController.sceneView = sceneView
selectedContentController.renderer(renderer, didUpdate: contentNode, for: anchor)
}
}
但是，我打印了faceAnchor.transform.columns.3，并使用True Depth相机获得了z负片.下面显示了x，y，z，w轴:
However, I printed faceAnchor.transform.columns.3 and obtained the z negative with True Depth camera. Below show x,y,z,w axis:
关于如何校正z轴的任何建议?预先谢谢你
Any suggestions on how to correct the z-axis? Thank you in advance
推荐答案
首先，让我们看看默认的矩阵值是什么.
At first, let's see what a default matrix values are.
这是具有默认值的Identity 4x4 matrix.
如果您需要有关4x4 matrices元素的其他信息，请阅读
If you need additional info on elements of 4x4 matrices read this post.
// 0 1 2 3
┌ ┐
| 1 0 0 0 | x
| 0 1 0 0 | y
| 0 0 1 0 | z
| 0 0 0 1 |
└ ┘
要翻转实体的Z axis和X axis，以便将轴从面部"跟踪环境重定向到世界"跟踪环境，请使用以下形式的4x4 transform matrix.
To flip entity's Z axis and X axis, in order to reorient axis from Face tracking environment to World tracking environment, use the following form of 4x4 transform matrix.
// 0 1 2 3
┌ ┐
| -1 0 0 0 | x
| 0 1 0 0 | y
| 0 0 -1 0 | z
| 0 0 0 1 |
└ ┘
在4x4 transform matrices中，旋转是 combination of scale and skew .要选择右旋方向，顺时针(CW)或逆时针(CCW)，对cos表达式使用+或-.
In 4x4 transform matrices rotation is a combination of scale and skew. To choose a right rotation's direction, clockwise (CW) or counter-clockwise (CCW) use + or - for cos expressions.
这是一个正Z旋转表达式(CCW).
Here's a positive Z rotation expression (CCW).
正数+cos(a):
┌ ┐
| cos -sin 0 0 |
| sin cos 0 0 |
| 0 0 1 0 |
| 0 0 0 1 |
└ ┘
这是一个负Z旋转表达式(CW).
And here's a negative Z rotation expression (CW).
负数-cos(a):
┌ ┐
|-cos -sin 0 0 |
| sin -cos 0 0 |
| 0 0 1 0 |
| 0 0 0 1 |
└ ┘
这篇关于将ARFaceAnchor从左手坐标系切换到右手坐标系的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
