ARKit将SCNNode放置在面向相机的位置 [英] ARKit Place a SCNNode facing the camera

问题描述

我正在使用 ARKit 来显示3D对象。我设法将节点放在用户面前的现实世界（也就是相机）。但是当我放下相机时，我无法让它们面对镜头。

I'm using ARKit to display 3D objects. I managed to place the nodes in the real world in front of the user (aka the camera). But I don't manage to make them to face the camera when I drop them.

let tap_point=CGPoint(x: x, y: y)
let results=arscn_view.hitTest(tap_point, types: .estimatedHorizontalPlane)
guard results.count>0 else{
    return
}
guard let r=results.first else{
    return
}

let hit_tf=SCNMatrix4(r.worldTransform)
let new_pos=SCNVector3Make(hit_tf.m41, hit_tf.m42+Float(0.2), hit_tf.m43)

guard let scene=SCNScene(named: file_name) else{
    return
}
guard let node=scene.rootNode.childNode(withName: "Mesh", recursively: true) else{
    return
}
node.position=new_pos
arscn_view.scene.rootNode.addChildNode(node)

节点位于相机前面的平面上。但他们都朝着同一个方向前进。我想我应该旋转 SCNNode ，但我没有设法做到这一点。

The nodes are well positioned on the plane, in front of the camera. But they are all looking in the same direction. I guess I should rotate the SCNNode but I didn't manage to do this.

推荐答案

首先，获取相机的旋转矩阵：

First, get the rotation matrix of the camera:

let rotate = simd_float4x4(SCNMatrix4MakeRotation(sceneView.session.currentFrame!.camera.eulerAngles.y, 0, 1, 0))

然后，结合矩阵：

let rotateTransform = simd_mul(r.worldTransform, rotate)

最后，将变换应用于您的节点，转换为SCNMatrix4：

Lastly, apply a transform to your node, casting as SCNMatrix4:

node.transform = SCNMatrix4(rotateTransform)

希望有所帮助

编辑

这里你如何从simd_float4x4创建SCNMatrix4

here how you can create SCNMatrix4 from simd_float4x4

   let rotateTransform = simd_mul(r.worldTransform, rotate)

  node.transform =  SCNMatrix4(m11: rotateTransform.columns.0.x, m12: rotateTransform.columns.0.y, m13: rotateTransform.columns.0.z, m14: rotateTransform.columns.0.w, m21: rotateTransform.columns.1.x, m22: rotateTransform.columns.1.y, m23: rotateTransform.columns.1.z, m24: rotateTransform.columns.1.w, m31: rotateTransform.columns.2.x, m32: rotateTransform.columns.2.y, m33: rotateTransform.columns.2.z, m34: rotateTransform.columns.2.w, m41: rotateTransform.columns.3.x, m42: rotateTransform.columns.3.y, m43: rotateTransform.columns.3.z, m44: rotateTransform.columns.3.w)

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