# The Mandelbrot Set

### byDaniel Shiffman (slight modification by l8l)

Simple rendering of the Mandelbrot set.

``````/**
* The Mandelbrot Set
* by Daniel Shiffman.
* (slight modification by l8l)
*
* Simple rendering of the Mandelbrot set.
*/

size(640, 360);
noLoop();
background(255);

// Establish a range of values on the complex plane
// A different range will allow us to "zoom" in or out on the fractal

// It all starts with the width, try higher or lower values
float w = 4;
float h = (w * height) / width;

// Start at negative half the width and height
float xmin = -w/2;
float ymin = -h/2;

// Make sure we can write to the pixels[] array.
// Only need to do this once since we don't do any other drawing.

// Maximum number of iterations for each point on the complex plane
int maxiterations = 100;

// x goes from xmin to xmax
float xmax = xmin + w;
// y goes from ymin to ymax
float ymax = ymin + h;

// Calculate amount we increment x,y for each pixel
float dx = (xmax - xmin) / (width);
float dy = (ymax - ymin) / (height);

// Start y
float y = ymin;
for (int j = 0; j < height; j++) {
// Start x
float x = xmin;
for (int i = 0; i < width; i++) {

// Now we test, as we iterate z = z^2 + c does z tend towards infinity?
float a = x;
float b = y;
int n = 0;
float max = 4.0;  // Infinity in our finite world is simple, let's just consider it 4
float absOld = 0.0;
float convergeNumber = maxiterations; // this will change if the while loop breaks due to non-convergence
while (n < maxiterations) {
// We suppose z = a+ib
float aa = a * a;
float bb = b * b;
float abs = sqrt(aa + bb);
if (abs > max) { // |z| = sqrt(a^2+b^2)
// Now measure how much we exceeded the maximum:
float diffToLast = (float) (abs - absOld);
float diffToMax  = (float) (max - absOld);
convergeNumber = n + diffToMax/diffToLast;
break;  // Bail
}
float twoab = 2.0 * a * b;
a = aa - bb + x; // this operation corresponds to z -> z^2+c where z=a+ib c=(x,y)
b = twoab + y;
n++;
absOld = abs;
}

// We color each pixel based on how long it takes to get to infinity
// If we never got there, let's pick the color black
if (n == maxiterations) {
pixels[i+j*width] = color(0);
} else {
// Gosh, we could make fancy colors here if we wanted
float norm = map(convergeNumber, 0, maxiterations, 0, 1);
pixels[i+j*width] = color(map(sqrt(norm), 0, 1, 0, 255));
}
x += dx;
}
y += dy;
}
updatePixels();
``````

This example is for Processing 4+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.