Processing: Creative Coding and Computational Art

concentric circles
size(200, 200);
background(255);
int x = width/2, y = height/2;
int w = 100, h = 100;
strokeWeight(4);
smooth();
fill(0);
arc(x, y, w-50, h-50, 0, PI*2);
noFill();
arc(x, y, w, h, 0, TWO_PI);
Figure 7-22. Creating circles with arc()
The arc() function’s first four arguments are identical to ellipse()’s arguments: x, y,
width, and height. You can also specify an ellipseMode() when using arc() to control
from what point the arc is drawn; the default mode is CENTER. The arc() function’s last
two arguments are the start and end angles of the arc’s rotation, specified in radians. If
you prefer to work in degrees, just convert the degrees to radians, using the
radians(angle) function. You’ll notice in my examples that I used PI as my value of rotation.
PI, in radians, specifies 180 degree rotation around an ellipse. PI*2, in radians, gives
one complete rotation (360 degrees). Processing actually has a constant for this as well:
TWO_PI, which I used in the second arc() statement.
Although arc() is easy to use, it is somewhat lacking as a general-purpose curve tool. For
example, to create a continuous curve path, it’s a little annoying trying to get a series of
arcs to line up. I’ll look at other Processing curve functions that do a better job with that.
One cool thing you can do with arc() is make wedge shapes. A not-so-exciting application
of this would be your standard pie chart. Here’s a simple example (shown in Figure 7-23):
CURVES
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