如何检测重叠的圆形并相应地填充颜色？

Question

我创建了5个圆形，使用3个数组（x，y和半径大小）随机选择x和y坐标和半径。但是，我需要圆圈根据是否与另一个圆圈重叠来动态更改颜色。所以如果5个圆圈中的一个完全不重叠，它应该被涂成黑色。重叠的圆应该是青色。如果两个圆的中心点之间的距离小于它们的半径之和，则认为两个圆重叠。

这是我迄今为圈子类写的。 以下代码将成功绘制小程序窗口中的5个圆圈，并且距离已成功计算，但问题与着色有关。颜色填充似乎存在逻辑错误，我在这里看不到问题。有什么建议么？非常感谢。

public class Circles extends Applet { 

public void paint(Graphics page) 
{ 
    Random locator = new Random(); 
    int [] xpt = new int [5]; 
    int [] ypt = new int [5]; 
    int [] rad = new int [5]; 

    setPreferredSize (new Dimension(300, 300)); 
    for (int i = 0; i < xpt.length; i++){ 

     xpt[i] = locator.nextInt(100); //need to set a number or it goes into millions, cannot set it in Random() 
     ypt[i] = locator.nextInt(100); 
     rad[i] = locator.nextInt(100); 
     System.out.println("The #" + i + " x-point: " + xpt[i] + " y-point: " + ypt[i] + " radius: " + rad[i]); //for debugging purposes 

     for (int j = 0; j < xpt.length; j++){ 
      double xpoint1 = xpt[i]+rad[i]; 
      double ypoint1 = ypt[i]+rad[i]; 
      double xpoint2 = xpt[j]+rad[j]; 
      double ypoint2 = ypt[j]+rad[j]; 
      double radius1 = rad[i]; 
      double radius2 = rad[j]; 
      double theDistance = distance(xpoint1,ypoint1,xpoint2,ypoint2); 
      System.out.println("Comparing " + i + " to " + j); //for debugging and logic checking 
      if (i==j) 
       ; 
      else if (theDistance <= (radius1+radius2)) 
      { 
       page.setColor(Color.cyan); 
       page.fillOval(xpt[i], ypt[i], rad[i], rad[i]); 
       //page.fillOval(xpt[j], ypt[j], rad[j], rad[j]); 
       System.out.println("Overlap occurred. Colored " + i + " and " + j + " cyan."); 
       System.out.println("Center points: ("+ xpoint1 +", "+ ypoint1 +") and ("+ xpoint2 + ", "+ ypoint2 + ")."); 
      } 
      else 
      { 
       page.setColor(Color.black); 
       page.fillOval(xpt[i], ypt[i], rad[i], rad[i]); 
       //page.fillOval(xpt[j], ypt[j], rad[j], rad[j]); 
       System.out.println("No overlap. Made " + i + " and " + j + " black."); 
      } 
     } 
    } 
} 

public static double distance(
     double x1, double y1, double x2, double y2) { 
    return Math.sqrt((x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1)); 

} 
} 

Answer 1

为什么你+rad[]在这里？您不必添加半径来比较距离。

 double xpoint1 = xpt[i]+rad[i]; 
     double ypoint1 = ypt[i]+rad[i]; 
     double xpoint2 = xpt[j]+rad[j]; 
     double ypoint2 = ypt[j]+rad[j]; 
[...] 
     double theDistance = distance(xpoint1,ypoint1,xpoint2,ypoint2); 
[...] 
     page.fillOval(xpt[i], ypt[i], rad[i], rad[i]); 

您应该使用xpt/ypt的距离。不xpoint1，并使用-的价值和2 *半径大小......即：

 double xpoint1 = xpt[i]-rad[i]; 
     double ypoint1 = ypt[i]-rad[i]; 
     double xpoint2 = xpt[j]-rad[j]; 
     double ypoint2 = ypt[j]-rad[j]; 
[...] 
     double theDistance = distance(xpt[i],ypt[i],xpt[j],ypt[j]); 
[...] 
     page.fillOval(xpoint1 , ypoint1, 2*rad[i], 2*rad[i]); 

Answer 2

的XPOINT，ypoint等线路是不是做你的想法。

如果要查找两个圆是否重叠，则需要查找圆的中心之间的距离是大于还是小于它们的半径之和。

所以：

function circlesCollide(x1, y1, r1, x2, y2, r2){ 
    return (distance(x1, y1, x2, y2) <= (r1 + r2)); 
}