【Java Swing】平面山脉实现

核心方法：递归

绘制平面山脉模型核心就是，画布上取两点，然后不断循环取横坐标中点，中点纵坐标取随机数，代码如下

​

public void recur(Graphics g, double x1, double x2, double y1, double y2, int range) {
            double x3 = (x1 + x2) / 2;
            double y3 = (y1 + y2) / 2;
            if (x2-x1<= 15) {
                g.drawLine((int) x1, (int) y1, (int) x3, (int) y3);
                g.drawLine((int) x2, (int) y2, (int) x3, (int) y3);
                return;
            }
            Random rand=new Random();
            int num=rand.nextInt(range);
            recur(g, x1, x3, y1, y3-num, range);
            recur(g, x3, x2, y3-num, y2, range);                    
        }

但是结果差强人意

很明显这并不像平面山脉，解决方案就在于我们需要每次递归时将纵坐标随机数值减小，，从而形成一种连绵起伏的效果，改进后代码如下

​

public void recur(Graphics g, double x1, double x2, double y1, double y2, int range) {
//range我用的是300，大家可以自己调节
            double x3 = (x1 + x2) / 2;
            double y3 = (y1 + y2) / 2;
            if (x2-x1<= 1|range==0) {
                g.drawLine((int) x1, (int) y1, (int) x3, (int) y3);
                g.drawLine((int) x2, (int) y2, (int) x3, (int) y3);
                return;
            }
            Random rand=new Random();
            int num=rand.nextInt(range*2)-range;
            range*=0.5;
            recur(g, x1, x3, y1, y3+num, range);
            recur(g, x3, x2, y3+num, y2, range);                    
        }

效果还是很接近真实山脉的

之后我们可以对山脉进行颜色填充美化，基于 Polygon 类，传入不同的透明度进行不同山脉的区别，代码如下

    public void recur(Graphics g, double x1, double x2, double y1, double y2, int range,int alp) {
        //实例range用的是300
        //四座山脉透明度分别为220，180，120，40
        double x3 = (x1 + x2) / 2;
        double y3 = (y1 + y2) / 2;
        if (x2-x1<= 1|range==0) {
            g.drawLine((int) x1, (int) y1, (int) x3, (int) y3);
            g.drawLine((int) x2, (int) y2, (int) x3, (int) y3);
            Polygon p=new Polygon();
            p.addPoint((int)x3, (int)y3);
            p.addPoint((int)x1, (int)y1);
            p.addPoint((int)x1, 800);
            p.addPoint((int)x2, 800);
            p.addPoint((int)x2, (int)y2);
            g.setColor(new Color(0,0,0,alp));
            g.fillPolygon(p);
            return;
        }
        Random rand=new Random();
        int num=rand.nextInt(range*2)-range;
        range*=0.5;
        //上面的0.5也可以改变，他控制的是循环次数和山脉的陡峭度，大家可以改变尝试
        recur(g, x1, x3, y1, y3+num, range,alp);
        recur(g, x3, x2, y3+num, y2, range,alp);
    }

大功告成，感谢观众老爷们阅读 ≧◇≦，如有错误，敬请指正