I'm sure you've all seen this in Powerpoint or Director but this nice effect is rarely seen in Flash: random pixels of an image appear successively until the entire image is shown. Although there are some difficulties associated
with randomization, this effect is still simple enough to grasp conceptually that it may be shown here. Using
a "maskee" movie clip as with the previous movie, you may add the following script to clip:
Now if you test the movie you should get a nice pixelated fade in effect: 5x5 pixel squares successively appear randomly on the screen. Now I don't expect you to understand every detail of the preceding script but it should
give you some hints on using dynamic masks to create fade-ins.
The main difficulty consists of randomly choosing the squares that will be
drawn on a given turn. Squares are numbered from the top left. An array is
created called choices which initially contains
the numbers
of all
the
squares.
At
some point in the enterFrame event, an element in
the array is randomly picked and kept in memory. A switch is made with the
last item in the
array and the array is popped, meaning the last element is removed. Then this
square is drawn on the screen.
As you see this script uses basically the same drawing routine as the previous
one but in a different context. It uses the same trick
as the first movie in creating the
mask: as long as the clear function is not called, everything that is drawn in the target clip is kept in memory and all subsequent shapes add up. This gives us a nice fade-in effect.
Always looking for a new challenge, I'm going to Senegal this summer to lend my computer skills in a volunteering project. I'm sending you this tutorial as part of my fundraising campaign, see http://dakar.netqcca.com . Enjoy!
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Dynamic masking using the drawing API
