如何使SCNNode面向ARAnchor

Question

我怎么能ARNode指向一个ARAnchor？

我想art.scnassets/ship.scn在屏幕中央使用显示并指向我刚刚放置在场景中的对象.

/// ViewController Class
func placeObject() {
    let screenCentre : CGPoint = CGPoint(x: self.sceneView.bounds.midX, y: self.sceneView.bounds.midY)
    guard let hitTestResult = sceneView.hitTest(screenCentre, types: [.featurePoint]).first else { return }

    // Place an anchor for a virtual character.
    let anchor = ARAnchor(name: identifierString, transform: hitTestResult.worldTransform)
    sceneView.session.add(anchor: anchor)
    // add to item model
    ItemModel.shared.anchors.append((identifierString, anchor)

}

func showDirection(of object: ARAnchor) { // object: saved anchor

    if !Guide.shared.isExist {
        let startPoint = SCNVector3(0, 0 , -1)
        let targetPoint = SCNVector3(object.transform.columns.3.x, object.transform.columns.3.y, object.transform.columns.3.z)

        let guideNode = Guide.shared.setPosition(from: startPoint, to: targetPoint)

        // add the ship in the center of the view
        sceneView.pointOfView?.addChildNode(guideNode)

    }
}
/// Guide Class   
func setPosition(from start: SCNVector3, to target: SCNVector3) -> SCNNode {
    isExist = true
    guideNode.position = start
    targetPosition = target

    // create target node from saved anchor
    let desNode = SCNNode()
    desNode.position = targetPosition

    let lookAtConstraints = SCNLookAtConstraint(target: desNode)
    guideNode.constraints = [lookAtConstraints]

    return guideNode
}

// MARK: - ARSCNViewDelegate
func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
    if let name = anchor.name, name.hasPrefix(identifierString) {
        // Create 3D Text
        let textNode: SCNNode = createNewBubbleParentNode(identifierString)
        node.addChildNode(textNode)
    }

}

我试过SCNLookAtConstraint但它没有按预期工作,有什么建议吗？

Answer 1

我注意到SCNLookAtConstraint当我的手机方向与地平线平行时，该功能有效。（屏幕朝上）

这行代码发挥了魔力！guideNode.pivot = SCNMatrix4Rotate(guideNode.pivot, Float.pi, 0, 1, 1)

如果您有兴趣，请参阅这里。

 public func showDirection(of object: arItemList) {

    guard let pointOfView = sceneView.pointOfView else { return }

    // remove previous instruction
    for node in pointOfView.childNodes {
        node.removeFromParentNode()
    }

    // target
    let desNode = SCNNode()
    let targetPoint = SCNVector3.positionFromTransform(object.1.transform)
    desNode.worldPosition = targetPoint

    // guide
    let startPoint = SCNVector3(0, 0 , -1.0)
    let guideNode = loadObject()
    guideNode.scale = SCNVector3(0.7, 0.7, 0.7)
    guideNode.position = startPoint

    let lookAtConstraints = SCNLookAtConstraint(target: desNode)
    lookAtConstraints.isGimbalLockEnabled = true
    // Here's the magic
    guideNode.pivot = SCNMatrix4Rotate(guideNode.pivot, Float.pi, 0, 1, 1)

    guideNode.constraints = [lookAtConstraints]
    pointOfView.addChildNode(guideNode)
}