相機沒有在Scenekit中跟隨飛機

Question

我有一架飛行中的飛機，我正在跟蹤，並且還顯示了飛機的跟蹤路線。我正在繪製圓柱體作爲繪製路徑的線條。它在2點之間繪製一條線。我有一個最初設置爲（0,200,200）的cameraNode。那時我可以看到飛機。但是當我開始我的飛行。它走出屏幕。我想要2件東西：

1. 只跟隨飛機（路徑無所謂）。
2. 顯示整個路徑和飛機。

我試圖找到最小廣告最大x，y和z和平均值，但它沒有工作。如果你看到下面的gif它太縮放和飛機已經移出屏幕

這是我如何設置我的相機：

- (void)setUpCamera { 
SCNScene *workingScene = [self getWorkingScene]; 
_cameraNode = [[SCNNode alloc] init]; 
_cameraNode.camera = [SCNCamera camera]; 
_cameraNode.camera.zFar = 500; 
_cameraNode.position = SCNVector3Make(0, 60, 50); 
[workingScene.rootNode addChildNode:_cameraNode]; 

SCNNode *frontCameraNode = [SCNNode node]; 
frontCameraNode.position = SCNVector3Make(0, 100, 50); 
frontCameraNode.camera = [SCNCamera camera]; 
frontCameraNode.camera.xFov = 75; 
frontCameraNode.camera.zFar = 500; 
[_assetActivity addChildNode:frontCameraNode]; //_assetActivity is the aircraft node. 

}

下面是我改變相機位置這是不工作：

- (void)showRealTimeFlightPath { 


DAL3DPoint *point = [self.aircraftLocation convertCooridnateTo3DPoint]; 
DAL3DPoint *previousPoint = [self.previousAircraftLocation convertCooridnateTo3DPoint]; 
self.minCoordinate = [self.minCoordinate findMinPoint:self.minCoordinate currentPoint:point]; 
self.maxCoordinate = [self.minCoordinate findMaxPoint:self.maxCoordinate currentPoint:point]; 
DAL3DPoint *averagePoint = [[DAL3DPoint alloc] init]; 
averagePoint = [averagePoint averageBetweenCoordiantes:self.minCoordinate maxPoint:self.maxCoordinate]; 

SCNVector3 positions[] = { 
    SCNVector3Make(point.x,point.y,point.z) , 
    SCNVector3Make(previousPoint.x,previousPoint.y,previousPoint.z) 
}; 
SCNScene *workingScene = [self getWorkingScene]; 
DALLineNode *lineNodeA = [[DALLineNode alloc] init]; 
[lineNodeA init:workingScene.rootNode v1:positions[0] v2:positions[1] radius:0.1 radSegementCount:6 lineColor:[UIColor greenColor]] ; 
[workingScene.rootNode addChildNode:lineNodeA]; 
self.previousAircraftLocation = [self.aircraftLocation mutableCopy]; 
self.cameraNode.position = SCNVector3Make(averagePoint.x, averagePoint.y, z); 
self.pointOfView = self.cameraNode; 

}

歡迎使用快捷或客觀的c代碼。

謝謝！

Answer 1

您描述的第一個行爲最容易通過鏈接瞄準飛機的查看約束和距離約束來實現。

let lookAtConstraint = SCNLookAtConstraint(target: aircraft) 

let distanceConstraint = SCNDistanceConstraint(target: aircraft) 
distanceConstraint.minimumDistance = 10 // set to whatever minimum distance between the camera and aircraft you'd like 
distanceConstraint.maximumDistance = 10 // set to whatever maximum distance between the camera and aircraft you'd like 

camera.constraints = [lookAtConstraint, distanceConstraint] 

對於iOS 10及更早版本，您可以使用SCNTransformConstraint實現距離約束。這是一個基本的（雖然稍微難看）的實現，它使用線性插值來更新節點的位置。

func normalize(_ value: Float, in range: ClosedRange<Float>) -> Float { 
    return (value - range.lowerBound)/(range.upperBound - range.lowerBound) 
} 

func interpolate(from start: Float, to end: Float, alpha: Float) -> Float { 
    return (1 - alpha) * start + alpha * end 
} 

let target = airplane 

let minimumDistance: Float = 10 
let maximumDistance: Float = 15 

let distanceConstraint = SCNTransformConstraint(inWorldSpace: false) { (node, transform) -> SCNMatrix4 in 
    let distance = abs(sqrt(pow(target.position.x - node.position.x, 2) + pow(target.position.y - node.position.y, 2) + pow(target.position.z - node.position.z, 2))) 

    let normalizedDistance: Float 

    switch distance { 
    case ...minimumDistance: 
     normalizedDistance = self.normalize(minimumDistance, in: 0 ... distance) 
    case maximumDistance...: 
     normalizedDistance = self.normalize(maximumDistance, in: 0 ... distance) 
    default: 
     return transform 
    } 

    node.position.x = self.interpolate(from: target.position.x, to: node.position.x, alpha: normalizedDistance) 
    node.position.y = self.interpolate(from: target.position.y, to: node.position.y, alpha: normalizedDistance) 
    node.position.z = self.interpolate(from: target.position.z, to: node.position.z, alpha: normalizedDistance) 

    return transform 
} 

第二行爲可以通過確定你的飛機的邊框和它的所有路徑段在相機的局部座標空間，然後從邊框的中心更新相機的距離幀的所有的實現視口中的那些節點。實現此功能的便利方法frameNodes(_:)在iOS 11中引入，並在SCNCameraController上定義。如果可能，我建議使用它，除非你想自己潛入三角。您可以使用您的場景視圖的默認相機控制器或創建一個臨時實例，以適合您的應用程序的需求。