iOS CATransform3D坐标

Question

真的很感激这方面的任何帮助.我在视图上应用了3D变换,需要识别渲染视图的边缘坐标,这样我就可以呈现与其相邻的另一个视图(没有任何像素间隙).具体来说,我希望通过动画角度来折叠像传单一样的一系列视图("页面").

    int dir = (isOddNumberedPage ? 1 : -1);
    float angle = 10.0;

    theView.frame = CGRectMake(pageNumber * 320, 0, 320, 460);        
    CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity;
    rotationAndPerspectiveTransform.m34 = -1.0 / 2000; // Perspective
    rotationAndPerspectiveTransform = CATransform3DRotate(rotationAndPerspectiveTransform, 
           dir * angle / (180.0 / M_PI), 0.0f, 1.0f, 0.0f);
    theView.layer.transform = rotationAndPerspectiveTransform;

    // Now need to get the top, left, width, height of the transformed view to correct the view's left offset

我通过检查CALayer尝试了很多方法,尝试使用我发现的一些矩阵数学代码片段失败,但是无法破解它甚至接近(取决于角度,一个好的20像素输出).有没有一种方法可以做到这一点,而无需花费2周阅读矩阵数学教科书？

Answer 1

视图的框架是superview坐标系中的轴对齐矩形.框架完全包围视图的边界.如果视图已转换,则框架会调整以紧密包围视图的新边界.

将Y轴旋转和透视应用于视图时,视图的左右边缘将移向其锚点(通常是视图的中心).左边缘也会变得更高或更短,而右边缘则相反.

因此视图的框架(应用变换后)将为您提供左边缘坐标和变换视图的宽度,以及较高边缘的顶部和高度(可能是左边缘或右边缘).这是我的测试代码:

NSLog(@"frame before tilting = %@", NSStringFromCGRect(self.tiltView.frame));
float angle = 30.0;
CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity;
rotationAndPerspectiveTransform.m34 = -1.0 / 2000; // Perspective
rotationAndPerspectiveTransform = CATransform3DRotate(rotationAndPerspectiveTransform, 
       1 * angle / (180.0 / M_PI), 0.0f, 1.0f, 0.0f);
self.tiltView.layer.transform = rotationAndPerspectiveTransform;
NSLog(@"frame after tilting = %@", NSStringFromCGRect(self.tiltView.frame));

这是输出:

2012-01-04 12:44:08.405 layer[72495:f803] frame before tilting = {{50, 50}, {220, 360}}
2012-01-04 12:44:08.406 layer[72495:f803] frame after tilting = {{62.0434, 44.91}, {190.67, 370.18}}

您还可以使用convertPoint:fromView:或在superview的坐标空间中获取视图角的坐标convertPoint:toView:.测试代码:

    CGRect bounds = self.tiltView.bounds;
    CGPoint upperLeft = bounds.origin;
    CGPoint upperRight = CGPointMake(CGRectGetMaxX(bounds), bounds.origin.y);
    CGPoint lowerLeft = CGPointMake(bounds.origin.x, CGRectGetMaxY(bounds));
    CGPoint lowerRight = CGPointMake(upperRight.x, lowerLeft.y);
#define LogPoint(P) NSLog(@"%s = %@ -> %@", #P, \
    NSStringFromCGPoint(P), \
    NSStringFromCGPoint([self.tiltView.superview convertPoint:P fromView:self.tiltView]))
    LogPoint(upperLeft);
    LogPoint(upperRight);
    LogPoint(lowerLeft);
    LogPoint(lowerRight);

输出:

2012-01-04 13:03:00.663 layer[72635:f803] upperLeft = {0, 0} -> {62.0434, 44.91}
2012-01-04 13:03:00.663 layer[72635:f803] upperRight = {220, 0} -> {252.713, 54.8175}
2012-01-04 13:03:00.663 layer[72635:f803] lowerLeft = {0, 360} -> {62.0434, 415.09}
2012-01-04 13:03:00.663 layer[72635:f803] lowerRight = {220, 360} -> {252.713, 405.182}

请注意,superLeft坐标系中upperLeft和upperRight点的Y坐标不同.