Re: CATransform3D perspective question
Re: CATransform3D perspective question
- Subject: Re: CATransform3D perspective question
- From: Nicko van Someren <email@hidden>
- Date: Sat, 1 Dec 2007 22:43:55 +0000
On 1 Dec 2007, at 17:10, John Harper wrote:
Presumably you did what the samples do and set the perspective
matrix as the sublayerTransform property of the superlayer of the
layer you're rotating?
Yes, that's right.
Both sublayerTransform and transform properties are applied relative
to the anchor point (typically center, though appkit sets the anchor
of layers it creates to the bottom left corner iirc) of the layer
the property is set on. So if you have two layers, one with a
perspective matrix, and its child rotated around the Y axis by 90°,
you will only see the child layer exactly edge on when its center is
aligned with the center of its superlayer. Does that explain what
you're seeing?
Aha. Thank you. That explains what I'm seeing exactly. The image
that was being rotated was off-centre in the layer that contained the
perspective transformation and turning it though 90 degrees left it
"pointing towards the origin" in the parent layer. Adding an
intermediate (empty) layer, moving the perspective transform up to the
intermediate layer and then centring the later containing the image to
be rotated in that layer now allows the image to rotate as I would
expect.
I've filled a bug report on the documentation for this, since there is
currently no description of the nature of the transformations that
take place.
Thanks again for the help,
Nicko
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