macos - 场景套件 - 拖动对象

Question

我正在尝试使用场景套件用鼠标/触控板拖动棋子。所有对象(棋盘和棋子)都是根节点的子节点，从 Collada 文件加载。

我找到了对 elsewhere on Stack Overflow 流程的有用描述。使用该描述，我编写了下面代码的初始版本。我的问题是点击坐标和片段节点位置之间的差异 - 它们的坐标是不同的数量级。我仍然不清楚如何将它们匹配——将它们放在“同一个宇宙”中。我尝试了 Apple 论坛上的一些建议以及我自己的想法。

这是我当前的尝试，大部分基于上面的链接恢复到原始版本，以及沿途记录的坐标值。结果是拖动棋子会导致它突然跳出屏幕:

- (NSPoint)
viewPointForEvent: (NSEvent *) event_
{
    NSPoint   windowPoint    = [event_ locationInWindow];
    NSPoint   viewPoint        = [self.view convertPoint: windowPoint
                                             fromView: nil];
    return viewPoint;
}

- (SCNHitTestResult *)
hitTestResultForEvent: (NSEvent *) event_
{
    NSPoint      viewPoint        = [self viewPointForEvent: event_];
    CGPoint      cgPoint        = CGPointMake (viewPoint.x, viewPoint.y);
    NSArray * points        = [(SCNView *) self.view hitTest: cgPoint
                                                     options: @{}];
    return points.firstObject;
}

- (void)
mouseDown: (NSEvent *) theEvent
{
    SCNHitTestResult * result = [self hitTestResultForEvent: theEvent];

    SCNVector3 clickWorldCoordinates = result.worldCoordinates;
      log output: clickWorldCoordinates x 208.124578, y -12827.223365, z 3163.659073
    SCNVector3 screenCoordinates = [(SCNView *) self.view projectPoint: clickWorldCoordinates];
    log output: screenCoordinates x 245.128906, y 149.335938, z 0.985565
    // save the z coordinate for use in mouseDragged
    mouseDownClickOnObjectZCoordinate = screenCoordinates.z;

    selectedPiece = result.node;  // save selected piece for use in mouseDragged

    SCNVector3    piecePosition = selectedPiece.position;
      log output: piecePosition x -18.200000, y 6.483060, z 2.350000

    offsetOfMouseClickFromPiece.x = clickWorldCoordinates.x - piecePosition.x;
    offsetOfMouseClickFromPiece.y = clickWorldCoordinates.y - piecePosition.y;
    offsetOfMouseClickFromPiece.z = clickWorldCoordinates.z - piecePosition.z;
    log output: offsetOfMouseClickFromPiece x 226.324578, y -12833.706425, z 3161.309073  
}

- (void)
mouseDragged: (NSEvent *) theEvent;
{
    NSPoint   viewClickPoint        = [self viewPointForEvent: theEvent];

    SCNVector3 clickCoordinates;
    clickCoordinates.x = viewClickPoint.x;
    clickCoordinates.y = viewClickPoint.y;
    clickCoordinates.z = mouseDownClickOnObjectZCoordinate;
      log output:  clickCoordinates x 246.128906, y 0.000000, z 0.985565

      log output:  pieceWorldTransform = 
      m11 = 242.15889219510001, m12 = -0.000045609300002524833, m13 = -0.00000721691076126, m14 = 0, 
      m21 = 0.0000072168760805499971, m22 = -0.000039452697396149999, m23 = 242.15890446329999, m24 = 0, 
      m31 = -0.000045609300002524833, m32 = -242.15889219510001, m33 = -0.000039452676995750002, m34 = 0, 
      m41 = -4268.2349924762348, m42 = -12724.050221935429, m43 = 4852.6652710104272, m44 = 1)

    SCNVector3 newPiecePosition;
    newPiecePosition.x = offsetOfMouseClickFromPiece.x + clickCoordinates.x;
    newPiecePosition.y = offsetOfMouseClickFromPiece.y + clickCoordinates.y;
    newPiecePosition.z = offsetOfMouseClickFromPiece.z + clickCoordinates.z;
      log output: newPiecePosition x 472.453484, y -12833.706425, z 3162.294639

    selectedPiece.position = newPiecePosition;
}

到目前为止，我已经收到了很多有趣且有用的评论和建议。但我意识到，要继续前进，我可能需要一个工作代码示例，它展示了允许点击和矢量存在于“同一个宇宙”中的 secret 武器。

Answer 1

你不需要“玩弄”来找到起源。您可以执行如下代码:

let originZ = sceneView.projectPoint(SCNVector3Zero).z
let viewLocation = /* Location in SCNView coordinate system */
let viewLocationWithOriginZ = SCNVector3(
  x: Float(viewLocation.x), // X & Y are in view coordinate system
  y: Float(viewLocation.y),
  z: originZ                // Z is in scene coordinate system
)
var position = sceneView.unprojectPoint(viewLocationWithOriginZ)
/* "position" is in the scene's coordinate system with z of 0 */