[iOS]學習筆記5（CATransform3D-Cube）

1. CATransform3D結構成員的意義。

struct CATransform3D
{
CGFloat m11（x縮放）, m12（y切變）, m13（旋轉）, m14（）;
CGFloat m21（x切變）, m22（y縮放）, m23（）, m24（）;
CGFloat m31（旋轉）, m32（）, m33（）, m34（透視效果，要操作的這個對象要有旋轉的角度，否則沒有效果。正直/負值都有意義）;
CGFloat m41（x平移）, m42（y平移）, m43（z平移）, m44（）;
}; 

ps:整體比例變換時，也就是m11==m22時，若m33>1，圖形整體縮小，若0<m33<1，圖形整體放大，若s<0,發生關於原點的對稱等比變換。

（）空的地方以后補充。

2. CATransform3DMakeTranslation

CATransform3DMakeTranslation(0, 0, 0) 創建了一個4*4的單位矩陣。

3. CATransform3DMakeRotation And CATransform3DRotate

CATransform3DMakeRotation()

    _transformedLayer = [CALayer layer];
    _transformedLayer.frame = self.bounds;
    _transformedLayer.anchorPoint = CGPointMake(0.5f, 0.5f);
    CATransform3D sublayerTransform = CATransform3DIdentity;
    // Set perspective
    sublayerTransform.m34 = kPerspective;
    [_transformedLayer setSublayerTransform:sublayerTransform];
    
    [self.layer addSublayer:_transformedLayer];
    //init Sublayers
    CATransform3D t = CATransform3DMakeTranslation(0, 0, 0);
    // take snapshot of the current view
    [_transformedLayer addSublayer:[self snapshot:t 
                                         withView:_contentView 
                                         isMasked:YES]];
    // 暫時先支持一個方向翻轉
    RotateDirection direction = RotateFromBottom;
    if (YES || direction == RotateFromBottom)
    {
        CGFloat height = self.bounds.size.height;
        //CGFloat cubeSize = 100.0f;
        t = CATransform3DRotate(t, D2R(90.0), 1, 0, 0);【1】
        t = CATransform3DTranslate(t, 0, height, 0);
        CALayer *subLayer = [self snapshot:t withView:view isMasked:YES];
        [_transformedLayer addSublayer:subLayer];
    }
    else 
    {
    }
    
    _newContentView = view;
    
    [self animationCubeRotate:direction withDuration:duration];

　　

4. 翻轉的動畫

- (void)animationCubeRotate:(RotateDirection)direction 
               withDuration:(float)duration
{
    [CATransaction flush];
    CGFloat height = self.bounds.size.height;
    CABasicAnimation *rotation;
    // CABasicAnimation *translationX;	// 如果沿X軸翻轉,則用不到這個變量.
    CABasicAnimation *translationY;	// 如果沿Y軸翻轉,則用不到這個變量.
    CABasicAnimation *translationZ;
    CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
    animationGroup.delegate = self;
    animationGroup.duration = duration;
    
    if ( direction == RotateFromBottom )
    {
        // 創建(某方向)關鍵幀動畫.
        translationY = [CABasicAnimation animationWithKeyPath:
                        @"sublayerTransform.translation.y"];
        translationY.toValue = [NSNumber numberWithFloat:-(height / 2)];【2】
        rotation = [CABasicAnimation animationWithKeyPath:
                    @"sublayerTransform.rotation.x"];
        rotation.toValue = [NSNumber numberWithFloat:D2R(-90.0f)];
    } 
    else if ( direction == RotateFromTop )
    {
    }
    
    // 處理Z軸
    translationZ = [CABasicAnimation animationWithKeyPath:
                    @"sublayerTransform.translation.z"];
    translationZ.toValue = [NSNumber numberWithFloat:height / 2];【3】
    animationGroup.animations = 
    	[NSArray arrayWithObjects: rotation, translationY, translationZ, nil];
    animationGroup.fillMode = kCAFillModeForwards;
    animationGroup.removedOnCompletion = NO;
    [_transformedLayer addAnimation:animationGroup forKey:kAnimationKey];
}

made, 我發現這個東西確實很難講清楚，主要是因為我理論薄弱，

【1】針對X軸旋轉，就是1，0，0，針對Y軸旋轉，就是0，1，0...下面那行也要進行正確的轉換。

【2】此處應該是和 anchorPoint有關系的。

【3】這個值會影響類似於深度的東西，比如說Cube會離我們更近，或者是更遠。（但是，似乎不算是透視關系）