Processing: Creative Coding and Computational Art

else {
}
// extra line needed to attach line back to point- ➥
not necessary in HATCHING style
line(x1, y1, x2, y2); //try commenting this line out
The HATCHING style doesn’t require this fix. Finally, you’ll notice that I use the same variable
name, steps, for the local variable in the makeRect() function and the parameter in
the scribble() function. I can do this because the steps variable is declared within the
makeRect() function, not at the top of the sketch. Therefore, it is local in scope to
the makeRect() function and not visible anywhere else. Thus, I can use the same-named
variable in both functions without any conflict. Of course, you can use unique names if
that seems simpler to you. Personally, I find it hard to keep coming up with new related
names, so I tend to reuse local variable names.
Well, enough of this low-level point recording business—let’s luxuriate through the rest of
this chapter using Processing’s user-friendly vertex() function.
Applying the vertex function
The vertex() function is called between the beginShape() and endShape() functions,
which internally take care of the point recording and rendering just discussed. You’ve
looked at the POINTS mode already. The LINES mode works similarly, except instead of
rendering points, vertices are connected by lines in groups of two. For example, the
following code generates a horizontal line:
size(300, 300);
background(255);
beginShape(LINES);
vertex(20, height/2);
vertex(width-20, height/2);
endShape();
Since the lines are laid down in groups of two vertices, adding a third vertex() function
call will have no effect on the output:
size(300, 300);
background(255);
beginShape(LINES);
vertex(20, height/2);
vertex(width-20, height/2);
vertex(width/2, height-20); //will have no effect
endShape();
LINES
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