Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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variables have global scope, meaning that they can be seen from anywhere within your
program, including within loops. In the earlier while loop example, the variable x has
global scope and can be seen anywhere in the program:
int x = 1000;
while (x>=0) {
println (x);
x -= 100;
}
Thus, you would not want to use x again as a counter in another loop later in the same
program, as it could cause unpredictable results. Because the for loop solves this problem
by keeping the counter variable local in scope, I tend to use for loops far more often than
while loops.
In the next section, “Functions,” I’ll go more into detail on local vs. global scope. Here are
a couple of other examples of for loops:
for (int i=1000; i>50; i-=2)
println(i);
}
for (int i=1000, j=200; i>50; i-=2, j++)
print("i = ");
println(i);
print("j = ");
println(j);
}
The top example is just a variation on the for loop discussed previously. It just counts
down by two instead of counting up by one. The second loop example uses multiple variables
and incrementors in the head—which is legal. You just separate the different
variables with commas. Try running this last loop example to view the output; it will help
you understand how the for loop runs.
for loops can add tons of efficiency to your code, and used cleverly can really cut down
on the number of code lines. As an example, I’ve recoded the stepped radial gradient (see
Figure 3-4) using a for loop, converting it into a smoother continuous gradient.
//Continuous radial gradient
size(200,200);
background(0);
for (int i=255; i>0; i--){
noStroke();
fill(255-i);
ellipse(width/2, height/2, i, i);
}