[Newbies] Creating a coverflow effect in Squeak

Ross Boylan RossBoylan at stanfordalumni.org
Sat Jun 14 17:03:22 UTC 2008

On Sat, 2008-06-14 at 13:43 +0200, Bert Freudenberg wrote:
> The path methods are a beautifully simple and useful, but they are  
> also a particularly bad example of Morphic programming.
Does this mean that they could be done properly in Morphic?  In other
words, is the problem here with Morphic, or with this particular

Or maybe it's just very difficult to do properly in Morphic?

I also have a more general question: if I'm not doing fancy animations
or 3D effects, are there any particular benefits or drawbacks of using
Tweak?  I was intrigued by some statements that Tweak has a clearer
separation of model and the graphical/interactive part (View/Controller
in MVC).  I definitely have separate model classes, and have found
Morphic a bit awkward for that reason.  It does have pluggable Morphs,

> You may notice how the entire World stops while you define a path  
> (have a clock morph running to see this). Also it uses Sensor  
> directly, and calls displayWorld. Both big no-nos in proper Morphic  
> programs. The followPath method even does the actual animation in a  
> background thread. Really Bad Things can happen if you do that.
> Tweak did set out to allow this kind of programming (because it is so  
> convenient), and it succeeded in that.
> For the original question - if you want the actual cover flow effect  
> you need a 3D renderer. You could use Croquet and OpenGL for that, but  
> it might be overkill. The Balloon3D render should be enough for this  
> simple type of animating.
> If you can live with a pseudo-3D effect (like the carousel seen on the  
> amazon.com frontpage) you can use simple 2D morphic animation of  
> course. In that effect, the covers always remain parallel to the  
> screen but only move position in a 3D circle so that they become  
> smaller in the back and larger in the front, and of course are sorted  
> back-to-front ...
> In fact, that is so simple I couldn't resist to make an etoy version,  
> 4 lines of code :)
> Uploaded as
> 	http://wiki.squeak.org/squeak/uploads/Carousel.pr
> - Bert -
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