Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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Inter-object collision
In the ActionScript book I mentioned earlier, Foundation ActionScript Animation: Making
Things Move! Keith Peters goes into glorious detail on the joys of billiard ball physics, or
what happens when objects collide, taking into account not only their velocity vectors but
their respective masses. This gets into a discussion on Newtonian physics, which is really
good stuff (stop making faces). However, as Keith has beat me to the punch (not to mention
that his elucidation on the subject rocks), and of course since we share the same publisher,
in this chapter I’ll include only some simple (and brief) examples dealing with the
subject. However, I strongly recommend that you check out Keith’s book to learn more.
Simple 1D collision
The simplest way to begin to understand these types of collisions is to move two balls
along a single axis in opposite directions, not taking into account any rotation, mass, drag,
wind, and so forth. In fact, we’ll begin with both balls moving at the same speed as well.
I’ve divided the sketch (shown in Figure 11-24) into five tabs: the main tab, the Ball class,
the Vect2D class, the checkBoundaryCollision() function, and the checkObjectCollision()
function. Of course, you can just put all the classes and functions in the main tab, below
the draw() function, instead. Here’s all the code, divided by tab:
// main sketch tab:
// 1D Collision with Swapping Velocities
Ball[] balls = {
new Ball(100, 200, 30), new Ball(300, 200, 30) };
Vect2D[] vels = {
new Vect2D(1.3, 0), new Vect2D(-1.3, 0) };
void setup(){
size(400, 400);
smooth();
noStroke();
}
void draw(){
background(255);
fill(150);
for (int i=0; i