Learning Processing: A Beginner's Guide to Programming Images ...

Mathematics 209
How quickly we increment t also aff ects the smoothness of the noise. Try running the code several times,
incrementing t by 0.01, 0.02, 0.05, 0.1, 0.0001, and so on.
By now, you may have noticed that noise( ) always returns a fl oating point value between 0 and 1. Th is
detail cannot be overlooked, as it aff ects how we use Perlin noise in a Processing sketch. Example 13-4
assigns the result of the noise( ) function to the size of a circle. Th e noise value is scaled by multiplying
by the width of the window. If the width is 200, and the range of noise( ) is between 0.0 and 1.0, the
range of noise( ) multiplied by the width is 0.0 to 200.0. Th is is illustrated by the table below and by
Example 13-4 .
Example 13-4: Perlin noise
float time = 0.0;
float increment = 0.01;
void setup() {
size(200,200);
smooth(); {
void draw() {
background(255);
float n = noise(time)*width;
Noise Value Multiplied by Equals
0 200 0
0.12 200 24
0.57 200 114
0.89 200 178
1 200 200
// With each cycle, increment the "time"
time + = increment;
Get a noise value at “time” and scale
it according to the window’s width.
// Draw the ellipse with size determined by Perlin noise
fill(0);
ellipse(width/2,height/2,n,n);
}
fi g. 13.4