int mx = 100;
int my = 100;

int nx = 200;
int ny = 150;

int r1 = 40;
int r2 = 30;
int r3 = 30;

void setup() {
  size(300,300);
  frameRate(25);
}
  
void draw() {
  background(0);
  loadPixels();
  for ( int y = 0; y < 300; y++ ) {
    for ( int x = 0; x < 300; x++ ) {
      
      int dx1 = x - mouseX;
      int dy1 = y - mouseY;

      int dx2 = x - mx;
      int dy2 = y - my;     

      int dx3 = x - nx;
      int dy3 = y - ny;     
       
      float d1 = dx1*dx1 + dy1*dy1;
      float d2 = dx2*dx2 + dy2*dy2;
      float d3 = dx3*dx3 + dy3*dy3;

      float f = fun( d1 / (r1*r1)) + fun( d2 / (r2*r2)) + fun(d3/(r3*r3));
      if (f > 0.4 && f < 0.6 ) {
        int c = (int)( fun( 3200 * (f-.5) * (f-.5)) * 255 );
        pixels[x + y * 300] = color(c);
      }      
    }  
  }
  updatePixels();
}

float fun( float xsq ) {
  float f = 0;
  if  ( xsq > -PI * 2 && xsq < PI * 2 ) {
    f = cos( xsq/2 ) * 0.5 + 0.5;
  }
  return f * f;
}