Graphics Reference
In-Depth Information
LISTING 5-4
-rotate3DTransform:
- (
IBAction
)rotate3DTransform:(
id
)sender;
{
NSValue
*value =
nil
;
CABasicAnimation
*animation =
nil
;
CATransform3D
transform;
[[
self
workLayer
]
removeAllAnimations
];
animation = [CABasicAnimation animationWithKeyPath:
@”transform”
];
transform =
CATransform3DMakeRotation
(1.57f, 1.0f, 1.0f, 0.0f);
value = [NSValue valueWithCATransform3D:transform];
[animation
setToValue
:value];
transform =
CATransform3DMakeRotation
(0.0f, 1.0f, 1.0f, 0.0f);
value = [NSValue valueWithCATransform3D:transform];
[animation
setFromValue
:value];
[animation
setAutoreverses
:
YES
];
[animation
setDuration
:1.0f];
[animation
setRepeatCount
:100];
[workLayer addAnimation:animation forKey:
kScaleKey
];
}
Listing 5-4 is nearly identical to Listing 5-3 except for the values passed into the
CATransform3DMakeRotation
method. This example sets both the
x
- and
y
-axes to
1.0
,
which produces a rotation on both axes and gives the illusion that the layer is flipping
diagonally.
Because we rotate the layer by 90 degrees and auto-reversing, this example appears to be
flipping all the way around on two axes. This would be useful when you have a two-sided
layer (such as a coin or a poker chip) and want to flip between its sides.
As previously mentioned in the discussion about layers, anchor points become extremely
important when dealing with transforms. When you apply a transform to a layer, the
transform uses the anchor point to determine where to rotate, scale, and so on.
With the examples so far, the scale transform (shown earlier in Listing 5-2) causes the
layer to appear to shrink into the middle of the window, as shown in Figure 5-2. This is
because the default position of the anchor point of any layer is the center.
However, if we alter -
applicationDidFinishLaunching:
and move the anchor point to
the lower-left corner of the layer, as shown in Listing 5-5, we get a dramatically different
effect.
