why do the circles disappear from the screen？

Question

Processing code as below, one quick question: why do the circles disappear from the screen when my mouse is playing with them? i've already add the boundary check however it does not seem to work. why???

int maxCircle = 200;
float minDistance=30;
float distance1;
float distance2;
Circle [] circles= new Circle[maxCircle];


void setup() {
  size(800,800);
  smooth();
  for(int i=0;i<maxCircle;i++){
    circles[i] = new Circle(random(width),random(height),random(2,20));
  }
}


void draw() {
  background(255,255);
  for(int i=0;i<maxCircle;i++) {
    circles[i].update(width,height);

    for (int j=0; j<maxCircle; j++) {
      distance1 = dist(circles[i].x,circles[i].y,circles[j].x,circles[j].y);
      if ( distance1 < minDistance ) {
        stroke(0,10);
        noFill();
        line(circles[i].x,circles[i].y,circles[j].x,circles[j].y);
       }
    }
    circles[i].display();
  }
}

void mouseMoved() {
  for(int i = 0; i<maxCircle;i++) {
    distance2 = dist(mouseX,mouseY,circles[i].x,circles[i].y);

    circles[i].x-=(mouseX-circles[i].x)/distance2;
    circles[i].y-=(mouseX-circles[i].y)/distance2;

    if(circles[i].x<circles[i].r || circles[i].x>width-circles[i].r) {
      circles[i].vx*=-1;
    };
    if(circles[i].y<circles[i].r || circles[i].y> height-circles[i].r) {
      circles[i].vy*=-1;
    }
  }
}    

class Circle {
  float x,y,vx,vy,r,speed;

  Circle(float tempx, float tempy, float tempr) {  
    x=tempx;
    y=tempy;
    vx=random(-1,1);
    vy=random(-1,1);
    r=tempr;
   }

  void update(int w,int h) {
    x+=vx;
    y+=vy;

    if(x<r || x>w-r) {
      vx*=-1;
    }
    if(y<r || y>h-r) {
      vy*=-1;
    }
   }

  void display() {
    fill(0,50);
    noStroke();
    ellipse(x,y,r,r);
  }
}

Just curious, can you give an idea of what you actually want this script to do? — muffinista, Sep 18 '12 at 14:54
@muffinista , i want to play with those cirecles. like i am tracing them and they are running away from me. but i want them always on the screen, instead of running away and disappear forever. — kikkpunk, Sep 18 '12 at 23:20

kikkpunk · Accepted Answer · 2012-10-06T11:31:37.503

Oh i found the solution:

   int maxCircle = 200;
   float minDistance = 20;
     Circle [] circles = new Circle[maxCircle];

void setup() {
size(800, 800);
smooth();
for (int i = 0; i < maxCircle; i++) {
  circles[i] = new Circle();
 }
}

  void draw() {
  background(255, 255);
     for (int i = 0; i < maxCircle; i++) {
circles[i].update(); 

noFill();
for (int j = 0; j < maxCircle; j++) {
  if (i == j)
    continue;


  float distance = dist(circles[i].x, circles[i].y, circles[j].x, circles[j].y);
  if (distance < minDistance) {
    stroke(0, 20);
    line(circles[i].x, circles[i].y, circles[j].x, circles[j].y);
  }
}

         circles[i].display();
    }
      }

 void mouseMoved() {
  for (int i = 0; i < maxCircle; i++) {
 float distance = dist(mouseX, mouseY, circles[i].x, circles[i].y);

circles[i].x -= (mouseX - circles[i].x) / distance;
circles[i].y -= (mouseX - circles[i].y) / distance;

circles[i].checkBounds();
      }
    }
     class Circle {
   float x, y, vx, vy, r, speed;

       Circle() {  
        vx = random(-1, 1);
         vy = random(-1, 1);
         r = random(1, 10); // See below
         x = random(r, width - r);
         y = random(r, height - r);  
     }

        void checkBounds() {
         if (x < r || x > width - r) {
           vx *= -1;
          if (x < r) {
           x = r;
           } else {
             x = width - r;
           }
           }
           if (y <= r || y >= height - r) {
           vy *= -1;
              if (y < r) {
                y = r;
             } else {
              y = width - r;
               }
            }
              }

        void update() {
x += vx;
y += vy;
checkBounds();
 }

   void display() {
     fill(0, 50);
      noStroke();

       ellipse(x, y, r * 2, r * 2);
      }
        }

I think it would be more useful to describe how you were able to solve the problem. You have modified the original source quite a bit and it is not clear what has been done. Other than adding functions and structure was there something wrong with the way they were calculating the bounds or was it something else? — JAMESSTONEco, Oct 06 '12 at 18:48

score 0 · Answer 2 · answered Oct 06 '12 at 19:06

in your update() method, when you calculate a new coordinate with your vector, you are potentially setting the coordinate offscreen. I have added 4 conditional statements that reset the value to the bounds of the screen if it exceeds it.

  void update(int w,int h) {
    x+=vx;
    y+=vy;

    if(x<r || x>w-r) {
      vx*=-1;
      if (x>w-r) x = w-r;
      if (x<r) x = r;
    }
    if(y<r || y>h-r) {
      vy*=-1;
      if (y>h-r) y = h-r;
      if (y<r) y = r;
    }
   }

why do the circles disappear from the screen？

2 Answers2