ios - 捏合(缩放)手势无法正确缩放

Question

我试图弄清楚为什么我的缩放在我的 OpenGL 相机上表现得很奇怪。它的目的是放大和缩小，但它的缩放非常随机。

这是我的代码:

- (void)pinchDetected:(UIPinchGestureRecognizer *)pinchRecognizer
{
    NSLog (@"%@", @"Pinching");

    if (pinchRecognizer.state == UIGestureRecognizerStateBegan ||
               pinchRecognizer.state == UIGestureRecognizerStateChanged ||
               pinchRecognizer.state == UIGestureRecognizerStateEnded) {
        currentScale = pinchRecognizer.scale;
    }

    if(lastScale < currentScale) {
       _camera.z += currentScale * 0.01f;
       lastScale = currentScale;
    } 

    if (lastScale > currentScale) 
    {
       _camera.z -= currentScale * 0.01f;
       lastScale = currentScale;
    }

}

Answer 1

如果你有一些乘法的东西并且你想把它变成加法，你需要取一个对数:

- (void)pinchDetected:(UIPinchGestureRecognizer *)pinchRecognizer
{
    if ((gesture.state == UIGestureRecognizerStateBegan) ||
        (gesture.state == UIGestureRecognizerStateChanged) ||
        (gesture.state == UIGestureRecognizerStateEnded)) {
        _camera.z += log(gesture.scale); // you'll probably want to multiply this by some constant
        gesture.scale = 1.0;
    }
}