在 ARKit 中放置、拖动和移除 SCNNode

Question

我正在使用 ARKit 做一个小项目。我希望能够在点击时将对象添加到我的 AR SceneView，双击删除它们，然后通过平移或拖动来拖动主题。

最初点击放置对象工作正常，但我在删除节点和拖动时遇到了一些问题。

删除和拖动的主要问题是很难真正“按住”或单击 SCNNode。大多数结果最终不在我添加的 SCNNode 上。

第二个问题是拖动有点麻烦，SCNNode 并没有像我的手指在拖动时那样真正移动。

我决定在github上创建一个项目，链接在这里：https://github.com/theraad/ARAttempt

但我也会在此处发布用于删除对象和拖动对象的代码：

-(void)handleRemoveObject:(UITapGestureRecognizer *)recognizer {
    NSLog(@"Long Press Fired");
    CGPoint tapPoint = [recognizer locationInView:_sceneView];

    NSArray <SCNHitTestResult *> *result = [self.sceneView hitTest:tapPoint options:nil];

    if ([result count] == 0) {
        return;
    }
    SCNHitTestResult *hitResult = [result firstObject];
    if (hitResult.node) {
        [[hitResult.node parentNode] removeFromParentNode];
    }
}

-(void)moveObject:(UIPanGestureRecognizer *)recognizer {
    NSLog(@"Move object");
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        NSLog(@"Pan state began");
        CGPoint tapPoint = [recognizer locationInView:_sceneView];
        NSArray <SCNHitTestResult *> *result = [self.sceneView hitTest:tapPoint options:nil];

        if ([result count] == 0) {
            return;
        }
        SCNHitTestResult *hitResult = [result firstObject];
        if ([hitResult.node.name isEqualToString:@"candle"]) {
            movedObject = [hitResult node];
        } else if ([[hitResult.node parentNode].name isEqualToString:@"candle"]) {
            movedObject = [[[hitResult node] parentNode] parentNode] parentNode];
        }
        if (movedObject){
            NSLog(@"Holding an Object");
        }
    }
    if (recognizer.state == UIGestureRecognizerStateChanged) {
        NSLog(@"Pan State Changed");
        if (movedObject) {

            CGPoint tapPoint = [recognizer locationInView:_sceneView];
            NSArray <ARHitTestResult *> *hitResults = [_sceneView hitTest:tapPoint types:ARHitTestResultTypeFeaturePoint];
            ARHitTestResult *result = [hitResults lastObject];

            SCNMatrix4 matrix = SCNMatrix4FromMat4(result.worldTransform);
            SCNVector3 vector = SCNVector3Make(matrix.m41, matrix.m42, matrix.m43);

            [movedObject setPosition:vector];
            NSLog(@"Moving object position");
        }
    }
    if (recognizer.state == UIGestureRecognizerStateEnded) {
        NSLog(@"Done moving object homeie");
        movedObject = nil;
    }
}

任何帮助将不胜感激。

谢谢。

更新：

所以我发现抓取物体的困难是因为我使用的是： self.sceneView.debugOptions = ARSCNDebugOptionShowFeaturePoints; 当我试图点击一个对象时，大多数时候它会抓住这些特征点之一。

-(void)moveObject:(UIPanGestureRecognizer *)recognizer {
    NSLog(@"Move object");
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        NSLog(@"Pan state began");
        CGPoint tapPoint = [recognizer locationInView:_sceneView];
        NSArray <SCNHitTestResult *> *result = [self.sceneView hitTest:tapPoint options:nil];

        if ([result count] == 0) {
            return;
        }
        SCNHitTestResult *hitResult = [result firstObject];
        movedObject = [[[hitResult node] parentNode] parentNode] parentNode]; //This aspect varies based on the type of .SCN file that you have
        }
        if (movedObject){
            NSLog(@"Holding an Object");
        }
    }
    if (recognizer.state == UIGestureRecognizerStateChanged) {
        NSLog(@"Pan State Changed");
        if (movedObject) {

            CGPoint tapPoint = [recognizer locationInView:_sceneView];
            NSArray <ARHitTestResult *> *hitResults = [_sceneView hitTest:tapPoint types:ARHitTestResultTypeFeaturePoint];
            ARHitTestResult *result = [hitResults lastObject];

            SCNMatrix4 matrix = SCNMatrix4FromMat4(result.worldTransform);
            SCNVector3 vector = SCNVector3Make(matrix.m41, matrix.m42, matrix.m43);

            [movedObject setPosition:vector];
            NSLog(@"Moving object position");
        }
    }
    if (recognizer.state == UIGestureRecognizerStateEnded) {
        NSLog(@"Done moving object homeie");
        movedObject = nil;
    }
}

所以问题似乎是我之前没有抓住整个对象，而是抓住了这个对象的一个​​孩子，当你试图拖动一个孩子时，它会由于某种原因迫使运动变得迟缓。所以我不得不做一些试验和错误来意识到我必须提升父母级别来解决这个问题。

希望这会有所帮助。

Answer 1

拖动对象的解决方法是将movedObject设置为[[[hitResult node] parentNode] parentNode] parentNode]，拖动变得更顺畅。