Processing: Creative Coding and Computational Art

* find distance for x and y
between prey and predator */
float deltaX = (pmouseX-x);
float deltaY = (pmouseY-y);
Since the ellipse and mouse are moving closer (until deltaX and deltaY eventually reach
0), we can be sure that the predator will never overshoot the prey. We can improve this
sketch by varying the speed in which the predator chases the prey with an effect called
easing. Easing simply adds some deceleration or acceleration to an object’s motion.
In the next example, I’ll have the predator decelerate as it nears the prey; this is also
referred to as easing out. Easing in would be the opposite—the predator would accelerate
toward the prey. To accomplish the easing out, I’ll add an easing variable that will work
very similarly to the damping variable used a few sketches back (shown in Figure 11-10).
// Ravenous Ellipse II
float x, y;
float easing = .05;
void setup(){
size(400, 400);
x = width/2;
y = height/2;
smooth();
}
void draw(){
// repaint background
fill(255, 40);
rect(0, 0, width, height);
}
/* find distance for x and y
between prey and predator */
float deltaX = (pmouseX-x);
float deltaY = (pmouseY-y);
// cause the predator to decelerate
deltaX *= easing;
deltaY *= easing;
x += deltaX;
y += deltaY;
ellipse(x, y, 15, 15);
MOTION
501
11