// Emergent Voronoi
// based on an algorithm presented by Coates
// Alasdair Turner 2010
PVector [] nodes;
PVector [] particles;
color [] colors;
PVector [][] field;
void setup()
{
size(400,400);
colorMode(HSB);
smooth();
nodes = new PVector [10];
colors = new color [4000];
particles = new PVector [4000];
field = new PVector [width][height];
reset();
frameRate(24);
}
void draw()
{
background(255);
noStroke();
fill(128);
for (int i = 0; i < nodes.length; i++) {
ellipse(nodes[i].x,nodes[i].y,20,20);
}
for (int i = 0; i < particles.length; i++) {
int x = round(particles[i].x);
int y = round(particles[i].y);
if (x > 0 && x < width && y > 0 && y < height) {
fill(colors[i]);
particles[i].add(field[x][y]);
ellipse(particles[i].x,particles[i].y,4,4);
}
}
}
void mousePressed()
{
reset();
}
void reset()
{
background(0);
for (int i = 0; i < nodes.length; i++) {
nodes[i] = new PVector(random(0,width),random(0,height));
}
for (int i = 0; i < particles.length; i++) {
colors[i] = color(random(255),random(204),204);
particles[i] = new PVector(random(0,width),random(0,height));
}
// Although this is perhaps against the spirit of
// an "emergent" voronoi pattern, I precalculate a
// vector field to move the particles
// If I had a massively parallel computer, I would
// be stricter, and let each particle determine its
// own distance from the nearest node. But I don't!
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
int nearest_node = -1;
float nearest_dist = 0.0f;
int nnearest_node = -1;
float nnearest_dist = 0.0f;
field[x][y] = new PVector();
for (int i = 0; i < nodes.length; i++) {
float d = dist(x,y,nodes[i].x,nodes[i].y);
if (nearest_node == -1 || d < nearest_dist) {
nnearest_node = nearest_node;
nnearest_dist = nearest_dist;
nearest_node = i;
nearest_dist = d;
}
else if (nnearest_node == -1 || d < nnearest_dist) {
nnearest_node = i;
nnearest_dist = d;
}
}
field[x][y] = new PVector(x-nodes[nearest_node].x,y-nodes[nearest_node].y);
field[x][y].mult(0.1*(nnearest_dist-nearest_dist)/(nnearest_dist+nearest_dist));
}
}
}

11 Feb 2010

I've just looked up Coates book on Amazon and think I'll be placing an order!!

I'm going to try coding this up using a background grid for faster spatial hashing.