Question

以下代码将节点放在摄像机前面，但始终位于距离摄像机位置10cm的中心位置。我想将节点放置在z方向上10厘米处，但是在触摸屏幕的位置的x和y坐标处。因此触摸屏幕的不同部分应该会导致节点放置在摄像机前方10厘米处，但位于触摸的x和y位置，而不是始终位于中心。

    var cameraRelativePosition = SCNVector3(0,0,-0.1)
    let sphere = SCNNode()
    sphere.geometry = SCNSphere(radius: 0.0025)
    sphere.geometry?.firstMaterial?.diffuse.contents = UIColor.white      
    Service.addChildNode(sphere, toNode: self.sceneView.scene.rootNode,    
    inView: self.sceneView, cameraRelativePosition:  
    cameraRelativePosition)

Service.swift

class Service: NSObject {

  static func addChildNode(_ node: SCNNode, toNode: SCNNode, inView:     
  ARSCNView, cameraRelativePosition: SCNVector3) {

    guard let currentFrame = inView.session.currentFrame else { return }
    let camera = currentFrame.camera
    let transform = camera.transform
    var translationMatrix = matrix_identity_float4x4
    translationMatrix.columns.3.x = cameraRelativePosition.x
    translationMatrix.columns.3.y = cameraRelativePosition.y
    translationMatrix.columns.3.z = cameraRelativePosition.z
    let modifiedMatrix = simd_mul(transform, translationMatrix)
    node.simdTransform = modifiedMatrix
    toNode.addChildNode(node)
  }
}

结果应如下所示：https://justaline.withgoogle.com

Answer 1

我们可以使用SCNSceneRenderer的unprojectPoint(_:)方法（SCNView和ARSCNView都符合此协议）将屏幕上的点转换为3D点。点击屏幕时，我们可以这样计算光线：

func getRay(for point: CGPoint, in view: SCNSceneRenderer) -> SCNVector3 {
    let farPoint  = view.unprojectPoint(SCNVector3(Float(point.x), Float(point.y), 1))
    let nearPoint = view.unprojectPoint(SCNVector3(Float(point.x), Float(point.y), 0))

    let ray = SCNVector3Make(farPoint.x - nearPoint.x, farPoint.y - nearPoint.y, farPoint.z - nearPoint.z)

    // Normalize the ray
    let length = sqrt(ray.x*ray.x + ray.y*ray.y + ray.z*ray.z)

    return SCNVector3Make(ray.x/length, ray.y/length, ray.z/length)
}

光线长度为1，因此通过将其乘以0.1并添加相机位置，我们得到您要搜索的点。

在触摸位置将相机放在相机前面

1 个答案: