Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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Figure 9-12. Toy Truck sketch
When looking at the code in the last example, I hope some of you protested, exclaiming
“Hey, you can’t use all those magic numbers!” It’s true, it isn’t good practice to use magic
numbers. And this really is a pretty lousy implementation of a truck (although it’s kind of
cute, don’t you think?). The problem I faced was dealing with all the accumulating matrix
transformations and having to manually plug in and try different values until I got my
truck. Because of the scaling effect, some of the translation values got pretty wacky, with
a few values far exceeding the display window dimensions. Fortunately, there is a much
better way to handle resetting the matrix values, which I’ll discuss shortly.
The last basic shape function I’ll cover is quad(). This function works just like the
triangle() function, but uses four vertices instead of three. The function requires eight
arguments, defining the x and y components of each of the four vertices. Unlike the
rect() function, in which each corner is 90 degrees, quad() can create a four-point polygon
with different angles for each corner. In the following simple quad() example, I illustrate
this using the random() function for each vertex (see Figure 9-13):
// Simple Quad
size(300, 300);
background(0);
noStroke();
smooth();
// quad(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y)
quad(50+random(-25, 25), 50+random(-25, 25), ➥
250+random(-25, 25), 50+random(-25, 25), ➥
250+random(-25, 25), 250+random(-25, 25), ➥
50+random(-25, 25), 250+random(-25, 25));