已知两点坐标，及在从其中一点开始移动的距离，求移动到的坐标

　//两点间距离  
    double dis = Math.pow(MathUtil.getDistanceSquare(list.get(i + 1).x, list.get(i + 1).y, list.get(i).x, list.get(i).y), 0.5);  
      
    // 计算斜率  
    double kx = (list.get(i + 1).x - list.get(i).x) / dis;  
    double kz = (list.get(i + 1).y - list.get(i).y) / dis;  
      
    //c为在两点间移动的距离  
    c = 2;  
      
    // 计算现在应该到达的距离  
    float x = (float) (list.get(i).x + (dis - (sumD - c)) * kx);  
    float z = (float) (list.get(i).y + (dis - (sumD - c)) * kz);  
      
    p.setX(x);  
    p.setY(nowPosition.getY());  
    p.setZ(z);  
      
    road.setIndex(i);  
      
    return p;