code: private static void randomGaussian( Random rand , double sigma , int radius , Point2D_I32 pt ) {
  
  		int x,y;
  
  		while( true ) {
  			x = (int)(rand.nextGaussian()*sigma);
  			y = (int)(rand.nextGaussian()*sigma);
  			if( Math.sqrt(x*x + y*y) < radius )
  				break;
  		}
  
  		pt.set(x,y);
  	}
docs: Randomly selects a point which is inside a square region using a Gaussian distribution.