my code not very well. sometimes weired, u see some ball stick to the boundary of large circle,why??

luotiantian234 · April 2015

ok

Chrisir · April 2015

again you didn't post correct

also we agreed that you ask for reflection on the inside of a circle

luotiantian234 · April 2015

i fix it,......now

luotiantian234 · April 2015

this time i post correctly.. :)

luotiantian234 · April 2015

my code did not work very well. sometimes weired, u will see some ball stick to the boundary of large circle,why?? how to fix it??

Silverjust · April 2015

I think, when some points get to fast, they go to deep into the "wall" and
won't go out with the reflection. so they reflect all the time
when they are updated.

Chrisir · April 2015

@SIlverjust:

what is the formula please to reflect a ball inside a circle?

Until this is answered properly, try the following:

the problem is the old stutter problem

I think it can be solved like this

check if dist to center >= radius

if so say (pseudo-code):

if (x < centerx) speedx = abs (speedx);
if (y < centery) speedy = abs (speedy);

if (x > centerx) speedx = -1*abs (speedx);
if (y > centery) speedy = -1*abs (speedy);

;-)

luotiantian234 · April 2015

@chrisir, i changed the code as u said like this, am i right? but still weired ..

 if (dist(x, y, width/2, height/2) > bandWidth ) {

      reset = true;
      xdirection *= -1;
      ydirection *= -1;
      xspeed+=random(-.4, .4);
      yspeed+=random(-.4, .4);
      if (x < centerx) xspeed  = abs (xspeed );
     if (y < centery) yspeed  = abs (yspeed );

     if (x > centerx) xspeed  = -1*abs (xspeed );
     if (y > centery) yspeed  = -1*abs (yspeed );
      reset = false;
    }

Chrisir · April 2015

no this works only when you use xspeed and yspeed without xdirection and ydirection anywhere in your code

luotiantian234 · April 2015

i have delete all the "xdirection and ydirection" as u said, but still weired, all the ball bounce once and disapeear...if u cope my code and see.

ArrayList<Agent> agents;
ArrayList<Point> frozen;
float diameter = 5;                   
int numAgents = 50  ;
float radius;
int bandWidth = 200;                  

void setup() {
  size (500, 500);
  background(255);
  frameRate(200);

  agents = new ArrayList();
  frozen = new ArrayList();
  radius=10;                         

  frozen.add(new Point(width/2, height/2));

  for (int i=0; i<numAgents; i++) {
    agents.add(new Agent());
  }
}

void draw() {
  background(255);
  stroke(0, 0, 255, 50 );                                
  noFill();
  ellipse(width/2, height/2, 2*radius, 2*radius);
  ellipse(width/2, height/2, 2*bandWidth, 2*bandWidth);

  if (agents.size()< 50) 
    agents.add(new Agent());

  Agent a; 
  for (int i=0; i<agents.size (); i++) {
    a = agents.get(i);
    a.run();
  }

  Point p;
  for (int i=0; i<frozen.size (); i++) {
    p = frozen.get(i);                         
    float[] pos = p.getPoint();
    stroke(0 );
    fill(0);
    ellipse(pos[0], pos[1], diameter, diameter);
  }
}


void mousePressed() {
  agents.add(new Agent());
}

class Agent {
  float x, y;
  boolean reset = false;
  float xspeed = 0.8 ;
  float yspeed = 0.8 ;
  //float xdirection =1 ;
  //float ydirection =1 ;
  float centerx;
  float centery;

  Agent() {
    if (radius<=bandWidth) {
      float r = random(radius, bandWidth );
      float a =random(TWO_PI);
      x = int (r*cos(a)+ width/2);
      y = int (r*sin(a)+ height/2);
    }
  }

  void run() {

    x+= xspeed  ;
    y+= yspeed  ;

    if (xspeed<-2) 
      xspeed=-2;
    if (xspeed>2) 
      xspeed=2;

    if (yspeed<-2) 
      yspeed=-2;
    if (yspeed>2) 
      yspeed=2;

    if (dist(x, y, width/2, height/2) > bandWidth ) {

     reset = true;
      //xdirection *= -1;
      //ydirection *= -1;
      xspeed+=random(-.4, .4);
      yspeed+=random(-.4, .4);
      if (x < centerx) xspeed  = abs (xspeed );
     if (y < centery) yspeed  = abs (yspeed );

     if (x > centerx) xspeed  = -1*abs (xspeed );
     if (y > centery) yspeed  = -1*abs (yspeed );
      reset = false;
    }


    fill(0, 255, 255);                                                                
    noStroke();
    ellipse(x, y, 8, 8);                                      


    float dist = dist(x, y, width/2, height/2); 

     //if (dist <= bandWidth ) {
    for (int i=0; i<frozen.size (); i++) {
      Point p = frozen.get(i);
      float[] pos = p.getPoint();

      float prox = diameter;
      if (dist(x, y, pos[0], pos[1]) < prox && radius<bandWidth-2) { 

        frozen.add(new Point(x, y));     
        x = pos[0] +(diameter*(x-pos[0]))/dist(x, y, pos[0], pos[1]);                   
        y = pos[1] +(diameter*(y-pos[1]))/dist(x, y, pos[0], pos[1]);

        fill(0);
        stroke(0);
        agents.remove(this) ;  
        break;
      }
    }
    //  }
  }
} 

          class Point {
  float[] pos = new float[2];                         
  float _x;
  float _y;

  Point( float _x, float _y) {
    pos[0]=_x;                                        
    pos[1]=_y;
    float d = dist(_x, _y, width/2, height/2);           
    radius = max(radius, d);
  }

  float[] getPoint() {
    return pos;
  }
}

Silverjust · April 2015

I don't know what's going on, but maby this helps.
the black line shows the speed of the agent. Every tick
he will move 1/10 of the line. When you press a key, it will update the agents.
when they touch the border of the window, they begin to switch between two states.

ArrayList<Agent> agents;
ArrayList<Point> frozen;
float diameter = 5;                  
int numAgents = 1  ;
float radius;
int bandWidth = 200;                 

void setup() {
  size (500, 500);
  background(255);
  frameRate(200);

  agents = new ArrayList();
  frozen = new ArrayList();
  radius=10;                        

  frozen.add(new Point(width/2, height/2));

  for (int i=0; i<numAgents; i++) {
    agents.add(new Agent());
  }
}

void draw() {
  background(255);
  stroke(0, 0, 255, 50 );                               
  noFill();
  ellipse(width/2, height/2, 2*radius, 2*radius);
  ellipse(width/2, height/2, 2*bandWidth, 2*bandWidth);

  if (agents.size()< 1)
    agents.add(new Agent());

  Agent a;
  for (int i=0; i<agents.size (); i++) {
    a = agents.get(i);
  //  a.run();
    a.draw();
  }

  Point p;
  for (int i=0; i<frozen.size (); i++) {
    p = frozen.get(i);                        
    float[] pos = p.getPoint();
    stroke(0 );
    fill(0);
    ellipse(pos[0], pos[1], diameter, diameter);
  }
}


void mousePressed() {
  agents.add(new Agent());
}
void keyPressed() {
  for (int i=0; i<agents.size (); i++) {
    Agent a = agents.get(i);
    a.run();
    a.draw();
  }
}

class Agent {
  float x, y;
  boolean reset = false;
  float xspeed = 0.8 ;
  float yspeed = 0.8 ;
  //float xdirection =1 ;
  //float ydirection =1 ;
  float centerx;
  float centery;

  Agent() {
    if (radius<=bandWidth) {
      float r = random(radius, bandWidth );
      float a =random(TWO_PI);
      x = int (r*cos(a)+ width/2);
      y = int (r*sin(a)+ height/2);
    }
  }

  void run() {

    x+= xspeed  ;
    y+= yspeed  ;

    if (xspeed<-2)
      xspeed=-2;
    if (xspeed>2)
      xspeed=2;

    if (yspeed<-2)
      yspeed=-2;
    if (yspeed>2)
      yspeed=2;

    if (dist(x, y, width/2, height/2) > bandWidth ) {

      reset = true;
      //xdirection *= -1;
      //ydirection *= -1;
      xspeed+=random(-.4, .4);
      yspeed+=random(-.4, .4);
      if (x < centerx) { 
        xspeed  = abs (xspeed );
        println(xspeed, yspeed, x, y);
      }
      if (y < centery) { 
        yspeed  = abs (yspeed );
        println(xspeed, yspeed, x, y);
      }

      if (x > centerx) { 
        xspeed  = -1*abs (xspeed );
      }
      if (y > centery) { 
        yspeed  = -1*abs (yspeed );
      }


      reset = false;
    }





    float dist = dist(x, y, width/2, height/2);

    //if (dist <= bandWidth ) {
    for (int i=0; i<frozen.size (); i++) {
      Point p = frozen.get(i);
      float[] pos = p.getPoint();

      float prox = diameter;
      if (dist(x, y, pos[0], pos[1]) < prox && radius<bandWidth-2) {

        frozen.add(new Point(x, y));    
        x = pos[0] +(diameter*(x-pos[0]))/dist(x, y, pos[0], pos[1]);                  
        y = pos[1] +(diameter*(y-pos[1]))/dist(x, y, pos[0], pos[1]);

        fill(0);
        stroke(0);
        agents.remove(this) ; 
        break;
      }
    }
    //  }
  }
  void draw() { 
    fill(0, 255, 255);
    noStroke();
    ellipse(x, y, 8, 8);    
    stroke(0);
    line(x, y, x+xspeed*10, y+yspeed*10);
  }
}

class Point {
  float[] pos = new float[2];                        
  float _x;
  float _y;

  Point( float _x, float _y) {
    pos[0]=_x;                                       
    pos[1]=_y;
    float d = dist(_x, _y, width/2, height/2);          
    radius = max(radius, d);
  }

  float[] getPoint() {
    return pos;
  }
}

luotiantian234 · April 2015

i created a new question to help understand my aim..

koogs · April 2015

what's up with this thread?

anyway: http://forum.processing.org/two/discussion/10179/how-to-make-the-ball-return-back-random-after-bouncing

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my code not very well. sometimes weired, u see some ball stick to the boundary of large circle,why??

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