Re: How to animate an object in a circle, but preserve it's orientation
Re: How to animate an object in a circle, but preserve it's orientation
- Subject: Re: How to animate an object in a circle, but preserve it's orientation
- From: Graham Cox <email@hidden>
- Date: Fri, 5 Jun 2009 14:04:44 +1000
On 05/06/2009, at 1:48 PM, Miles wrote:
Thanks for the quick response!
I've mostly been reading trying to see what would work. I did mess
with changing the anchorPoint to get the initial animation route,
but that didn't seem to suffice.
The object I'm animating is a simple UIView containing an image.
I thought about the timer approach like you mention, the reason I
shy'd away from it was that it needs to stay in sync with another
animating object (in my ferris wheel example this would be the wheel
itself.)
But now that I think of it I might be able to use the timer to
animate that as well so they do stay in sync.
Does that seem like the best and/or easiest approach?
Well, I'd say it can be made to work, but I personally wouldn't do it
this way.
It's still a bit vague, but I'm visualising a Ferris Wheel with a
number of (one or more) attached basket objects. To model this, I
would define the angle and radius as properties of the wheel, and the
position of the basket as a property in terms of its position relative
to the wheel (a fixed angle, say). The basket objects could be owned
by the wheel, which makes good sense to me.
To animate the rotation of the wheel, simply increment the angle of
the wheel. This in turn directly or indirectly updates the positions
of its attached baskets. The whole thing is then redrawn in the new
position. The absolute location of a basket can be simply calculated
as needed when the basket is drawn, based on the wheel's angle, radius
and relative position of the basket on the wheel.
Any time I hear people talking about "keeping things in sync" alarm
bells ring. Instead, make one property a derivative or dependency of
the other, then there is nothing to 'sync', it's always in sync.
In terms of visualising the wheel/basket model in a view, I'd just use
a custom view and drawn the entire content. The wheel object could
draw itself, which in turn calls on each of its basket objects to draw
themselves, and so on. Trying to make each basket a separate view will
be inefficient and more complicated than this.
--Graham
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