Processing: Creative Coding and Computational Art

This is the same drawTable() function as in the last example, only many of the values in
the main algorithm have been converted into parameters. Parameters are the variables,
including their type declaration, that are placed between the parentheses of a function
head when a function is defined. When you call or invoke the function, the values you pass
to the function parameters are referred to as arguments. This can be confusing to new
coders. The parameters define the number and type of arguments the function requires to
be called. Another term you may come across is the function signature, which is just the
name of the function, its parameters, and the return type. The return type relates to what,
if any, value the function returns. A function that doesn’t return any value has a void
return type. You always need to specify either a return type or void when you define a
function. That’s why both the setup() and drawTable() functions are prefaced by the
void keyword. Functions that return a specific value need to be prefaced by the data type
of that value. For example, to return an int, a function should be prefaced with int. The
same rule holds true for any data type that a function returns. Functions may return any
legal data type.
The parameters in the new, improved drawTable() function open up a ton of cool possibilities,
a few of which you can see in the included figures. Try changing any of the following
argument values to see what happens: cols, rows, xPadding, yPadding, randomFactor,
colorMin, strokeWtMax, and overDraw. You can change these values at the top of the
setup() function, before the drawTable() function call is made. Really take the time to
experiment with this sketch. It covers a lot of stuff you’ll see again and again. I also think
you’ll be surprised at the range of output you can get with relatively few lines of code
(although I realize that this might look like a lot of code to some of you).
In the next section, you’ll look at the vertex() function, along with the companion
beginShape() and endShape() functions. Using the vertex() function opens up even
more exciting possibilities.
Vertex functions
A vertex is just another word for a point. However, what separates the vertex() function
from the point() function is that the vertex() function utilizes the companion
beginShape() and endShape() functions, allowing the vertices to be connected into lines,
curves, 2D shapes, and even 3D forms. Since coordinate locations in a Cartesian system
require a coordinate component for each axis, it makes sense that any form plotted on the
computer would be reducible to a series of point locations, or vertices. The beginShape()
function takes a mode argument that controls how the vertices are joined. The seven
mode arguments are POINTS, LINES, TRIANGLES, TRIANGLE_STRIP, TRIANGLE_FAN, QUADS,
and QUAD_STRIP. (Please note that POINTS mode is no longer documented in the official
language API, but continues to work as of this writing.) If no option is specified, the line
strip mode is used, which can be closed to form a polygon. This chapter will only look at
how to use these modes to generate points, lines, open line strips, and closed line strips
(polygons).
LINES
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