从 didAdd 锚点获取 ARAnchor 的旋转答案

【问题标题】：Getting rotation of ARAnchor from didAdd anchors从 didAdd 锚点获取 ARAnchor 的旋转
【发布时间】：2020-02-11 00:30:18
【问题描述】：

所以我使用session(_ session: ARSession, didAdd anchors: [ARAnchor] 来获取所有检测到的平面（我不能使用renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor)，因为我使用的是RealityKit 而不是ARKit）。

所以我的问题是，如何通过这种方法获得检测到的锚点的旋转？我想创建一个平面实体，它与检测到的锚点具有完全相同的位置、大小、方向和旋转。到目前为止，我使用大小的范围，位置的中心，但我不知道如何获得旋转。因为现在它检测到正确（正确的位置和大小）但与真实平面的旋转错误。

【问题讨论】：

@ARGeo 你知道答案吗？

标签： scenekit arkit realitykit

【解决方案1】：

您可以从 ARPlaneAnchor 的 transform 属性中获取位置和方向，然后使用它在 RealityKit 中渲染边界平面。

extension float4x4 {

  /// Returns the translation components of the matrix
  func toTranslation() -> SIMD3<Float> {
    return [self[3,0], self[3,1], self[3,2]]
  }

  /// Returns a quaternion representing the 
  /// rotation component of the matrix
  func toQuaternion() -> simd_quatf {
    return simd_quatf(self)
  }
}

func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {

  guard let planeAnchor = anchors[0] as? ARPlaneAnchor else {
    return
  }

  // NOTE: When the ARPlaneAnchor is first created its transform
  // contains the position and the plane.center == [0,0,0]. On updates
  // the plane.center will change as the extents of the plane change.
  let position = planeAnchor.transform.toTranslation()
  let orientation = planeAnchor.transform.toQuaternion()

  // The center is a position before the orientation is taken in to
  // account, so we need to rotate it  to get the true position before
  // we add it to the anchors position
  let rotatedCenter = orientation.act(planeAnchor.center)

  // You have a ModelEntity that you created earlier
  // e.g. modelEntity

  // Assuming you added the entity to an anchor that is just 
  // fixed at 0,0,0 in the world, or you created a custom entity
  // with HasAnchor set to 0,0,0
  modelEntity.transform.translation = position + rotatedCenter
  modelEntity.transform.rotation = orientation

  // Doesn't seem to be a way to update meshes in RealityKit so
  // just create a new plane mesh for the updated dimensions
  modelEntity.model?.mesh = MeshResource.generatePlane(
    width: planeAnchor.extent.x, 
    depth: planeAnchor.extent.z
  )
}

【讨论】：