从画布中心开始爆炸

Question

我有一个画布设置，我试图找出一个方程式，使圆圈从原点开始出现，然后在随机位置增加边界。我在绘画中绘制了这个图像，以帮助解释我想要发生的事情

这是从右上角和左上角绘制两个爆炸的循环：

for (iii = 0; iii <= 6000; iii++)
{

    graphics.setColor(colors[c1]);//same color as comet

    a1 = ((int)(Math.random() * iii/10));
    a2 = ((int)(Math.random() * iii/10 ));
    a3 = ((int) (Math.random()* 15 + 1));
    graphics.drawOval(a1, a2, a3, a3);

    graphics.setColor(colors[c2]);//same color as comet

    a2 = ((int)(Math.random() * iii/10 ));
    a1 = 600 - ((int)(Math.random() * iii/10));

    a3 = ((int) (Math.random()* 20 + 1));
    graphics.drawOval(a1, a2, a3, a3);
    try 
    {
        TimeUnit.NANOSECONDS.sleep(1);///change to higher #
    } // end try
    catch (Exception e) 
    {
        System.out.println("Exception caught");
    } // end catch

以下是：

的图片

我不是要求别人为我编写代码，我只是无法弄清楚如何去做，并且可以在正确的方向上使用一点点。

Answer 1

a1 = screenWidth - (int)((Math.random()-0.5)*iii/10);
...
graphics.drawOval(a1-a3/2, a2-a3/2, a3, a3);

Answer 2

继承人我最终做的事情：

for (iii = 0; iii <= 6000; iii++)
            {
                //random sized, random colored circles explosion
                c3 = ((int)(Math.random()*8));
                graphics.setColor(Color.BLACK);
                a1 = 300-iii/10 +(2*((int)(Math.random()*iii)))/10;//x coordinate
                a2 = 300-iii/10 +(2*((int)(Math.random()*iii)))/10;//y coordinate
                a3 = ((int) (Math.random()* 15 + 1));   //size (length = width)
                graphics.fillOval(a1, a2, a3, a3);      //center of circle black
                graphics.setColor(colors[c3]);          //randomly selected color
                graphics.drawOval(a1, a2, a3, a3);      //outline of circle

                try 
                {
                    TimeUnit.MILLISECONDS.sleep(3);
                } // end try
                catch (Exception e) 
                {
                    System.out.println("Exception caught");
                } // end catch

            }//end for center explosions

Answer 3

public void explosion(final float XCenter, final float YCenter, final int rad) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            Random rand = new Random();
            for (int i = 0; i <= rad; i++) {
                int degree = rand.nextInt(359);
                int x = XCenter + (float) (Math.cos(degree * 3.141592 / 180) * i);
                int y = YCenter + (float) (Math.sin(degree * 3.141592 / 180) * i);
                int size = ((int) (Math.random() * 15 + 1));
                int color = Color.rgb(rand.nextInt(254), rand.nextInt(254), rand.nextInt(254));
                graphics.setColor(color);         
                graphics.drawOval(x, y, size, size);
                try {
                    Thread.sleep(1);
                } catch (Exception e) {
                }
            }
        }
    }).start();
}