Re: Group CGAffineTransform Animations?
Re: Group CGAffineTransform Animations?
- Subject: Re: Group CGAffineTransform Animations?
- From: WT <email@hidden>
- Date: Wed, 17 Jun 2009 17:16:46 +0200
On Jun 17, 2009, at 4:37 PM, Graham Cox wrote:
It's fair to say that transforms can be a bit unintuitive - you
expect them to perform the operations in the order you set. In fact,
the reverse order is what it will actually do. (The explanation for
this lies in the maths, but it sounds like you're not interested in
that, in which case this might be a struggle).
For people with a background closer to programming and farther from
math, it might be easier to think of matrix multiplication as a stack
(the LIFO kind of data structure). What you write last is what gets
done first when it comes to using matrices as operations on
geometrical objects. So, the result of applying ABC to an object o
(where A, B, and C are matrices) is that first C is applied to o, then
B is applied to the result of that, then A is applied to the result of
*that*. In reality, behind the curtains, it may be and often is the
case that A, B, and C get multiplied together first and then the
result of that is applied to o, but conceptually you can think of it
as I described.
Wagner
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