On 10 Nov 2008, at 10:07 pm, Kyle Sluder wrote:
On Mon, Nov 10, 2008 at 5:56 AM, Graham Cox <[EMAIL PROTECTED]>
wrote:
Yet you need to do this all the time if you do rotation of anything
at all.
Rotation around the origin is almost never in itself useful.
Eh, I beg to differ. Rotation about the origin is one of the most
common operations in 3D graphics, since you typically treat the origin
as model space and just do one final translation to get your models
into world space. This is essentially what OpenGL does when you build
your model and world transformation stacks.
--Kyle Sluder
Well, I defer to your expertise in 3D - not my area. But certainly in
2D with typical Cocoa objects you are usually concerned with
positioning paths or text at some point in your view. I don't think
I've ever done a rotation that didn't translate to some point and back
again. You can of course think of this as moving the origin and thus
you are *always* rotating about the origin, but I'd hazard a guess
that most people are more comfortable with the idea of rotating some
object about an arbitrary point. Hence the OP's method, which is
identical in spirit to several I use constantly.
--Graham
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