pakt08
See /f0blog/pact-februari/
//pakt08 not the exact correct filling rule
int n;
float d, speed, spread, theta;
float[][] pnts;
void setup() {
size(640, 480, JAVA2D);
frameRate(60);
n= 25;
d= 0.0001;
speed= 0.00002;
spread= 2.0;
theta= 0.0;
pnts= new float[n][2];
for (int i= 0; i<n; i++) {
pnts[i][0]= width*0.5;
pnts[i][1]= height*0.5;
}
fill(255.0, 0.0, 0.0);
blendMode(DIFFERENCE);
noStroke();
}
void draw() {
background(0);
float xx= width*0.5, yy= height*0.5;
beginShape();
for (int i= 0; i<n; i++) {
float c= cos(theta+(i*d));
float s= sin(theta+(i*d));
float x= (pnts[i][0]/width)*2.0-1.0;
float y= (pnts[i][1]/height)*2.0-1.0;
float vx= (((c*x)-(s*y))*0.5+0.5)*width+spread;
float vy= (((c*y)+(s*x))*0.5+0.5)*height+spread;
pnts[i][0]= vx;
pnts[i][1]= vy;
vertex(xx, yy);
xx= vx;
yy= vy;
theta= theta+speed;
}
endShape();
}