I'd like to draw a line connecting the middle of each of the circles when they touch only. I have managed to make a simple method for highlighting each circle when they touch. I just don't know how to calculate and draw a line between these two objects when highlighted (touching). Any help would be much appreciated.

Here's the code:


Agents agent1;
 Agents agent2;
 float x;
 float y;
 float angle = 0.0; // Direction of motion  
 float speed = 1.4; // Speed of motion

void setup() {
 
 size(700, 400);
 background(255);
 smooth();
 frameRate(25);
 
 agent1 = new Agents(200,200,150,speed,angle);
 agent2 = new Agents(200,200,175,5,angle);
}

void draw() {

 background(255);
 agent1.move();
 agent2.move();
 
 if (agent1.nearanotherAgent(agent2)) {
 agent1.highlight();
 agent2.highlight();
 
 }

 agent1.display();
 agent2.display();
 
}

class Agents {
 
 float x,y;
 float diameter;
 float speed;
 float angle;
 color c = color(0);
 
 
 Agents(float xpos, float ypos, float dia, float sp, float dir) {
   
   x = xpos;
   y = ypos;
   diameter = dia;
   speed = sp;
   angle = dir;
   
 }
 
 
 void move() {
   
  angle += random(-0.13, 0.13);
  x += cos(angle) * speed;
  y += sin(angle) * speed;
 
    if(x >= width+diameter/2) {
       x = 0.0;
     }  

     if(y >= height+diameter/2) {
       y = 0.0;  
     }
     
     if(x <= 0.0-diameter/2) {
      x = width + diameter;
     }  
     
     if(y <= 0.0-diameter/2) {
      y = height;
     }
 }
 
 void highlight() {
   c = color(255,0,0);
   
 }
 
 void display() {
   
   stroke(c);
   noFill();
   ellipse(x,y,diameter,diameter);
   c = color(0);
   
 }
 
  boolean nearanotherAgent(Agents b) {
  return dist(x,y,b.x,b.y)<=diameter;
 }
}

Thank you for your reply and advice PhiLho. I'm still at a loss however on how to calculate the center of each ellipse and the distance between each, as well as keeping that information up to date  throughout the animation. I'm guessing that this information is what I need to call in the line's x,y coordinates and length variables? Any snippets of code may well help me out. Thank you.

Code:

Agent agent1;
Agent agent2;
float x;
float y;
float angle = 0.0; // Direction of motion  
float speed = 1.4; // Speed of motion

void setup() {
 
 size(700, 400);
 background(255);
 smooth();
 frameRate(25);
 
 agent1 = new Agent(200,200,150,speed,angle);
 agent2 = new Agent(200,200,175,5,angle);
}

void draw() {

 background(255);
 agent1.move();
 agent2.move();
 
 if (agent1.nearAnotherAgent(agent2)) {
   agent1.highlight();
   agent2.highlight();
 
 }

 agent1.display();
 agent2.display();
 
}

class Agent {
 
 float x,y;
 float diameter;
 float speed;
 float angle;
 color c = color(0);
 Agent nearAgent;
 
 
 
 Agent(float xpos, float ypos, float dia, float sp, float dir) {
   
   x = xpos;
   y = ypos;
   diameter = dia;
   speed = sp;
   angle = dir;
 }

 void move() {
  angle += random(-0.13, 0.13);
  x += cos(angle) * speed;
  y += sin(angle) * speed;
 
    if(x >= width+diameter/2) {
	 x = 0.0;
     }  

     if(y >= height+diameter/2) {
	 y = 0.0;  
     }
     
     if(x <= 0.0-diameter/2) {
	x = width + diameter;
     }  
     
     if(y <= 0.0-diameter/2) {
	y = height;
     }
 }
 
 void highlight() {
   c = color(255,0,0);
   if (nearAgent != null) {
     stroke(#FF0000);
     line(x, y, nearAgent.x, nearAgent.y);
   }
 }
 

 void display() {
   stroke(c);
   noFill();
   ellipse(x,y,diameter,diameter);
   c = color(0);
 }
 
  boolean nearAnotherAgent(Agent b) {
    boolean near = dist(x,y,b.x,b.y) <= diameter;
    if (near) {
	nearAgent = b;
    } else {
	nearAgent = null;
    }
    return near;
 }
} 

Ok, I bet you knew this question was coming didn't you? Well, I don't really have a question here, rather I'm pulling my hair out trying to get my head around implementing an array of agents with this code. I don't understand what I'm doing wrong after many a search...clueless I am!


int numAgents = 5;

Agent[] ag = new Agent [numAgents];

float x;
float y;
float angle = 0.0; // Direction of motion  
float speed = 1.4; // Speed of motion
float diameter = 0.0;

void setup() {

size(700, 400);
background(255);
smooth();
frameRate(25);
//float rad = random(5.0,150.0);

for (int i = 0; i < ag.length; i++) {
ag[i] = new Agent(200,200,speed,angle);

}
}


void draw() {

background(255);
for (int i = 0; i < ag.length; i++) {

ag[i].move();

if (ag[i].nearAnotherAgent(ag[i])) {
  ag[i].highlight();
}
ag[i].display();

}
}


//--------------------------------------------------------------------------

class Agent {

float x,y;
float diameter;
float speed;
float angle;
color c = color(0);
Agent[] nearAgent;

//--------------------------------------------------------------------------


  Agent(float xpos, float ypos, float sp, float dir) {
 
  x = xpos;
  y = ypos;
  diameter = random(5.0,150.0);
  speed = sp;
  angle = dir;

}

//--------------------------------------------------------------------------

void move() {
 angle += random(-0.13, 0.13);
 x += cos(angle) * speed;
 y += sin(angle) * speed;

   if(x >= width+diameter/2) {
      x = 0.0;
    }  

    if(y >= height+diameter/2) {
      y = 0.0;  
    }
   
    if(x <= 0.0-diameter/2) {
     x = width + diameter;
    }  
   
    if(y <= 0.0-diameter/2) {
       y = height;
    }
}

//--------------------------------------------------------------------------

void highlight() {
  c = color(0,0,255);
  for (int i = 0; i < ag.length; i++) {
  if (nearAgent[i] != null) {
    stroke(c);
    line(x, y, nearAgent[i].x, nearAgent[i].y);
  }
}
 }

//--------------------------------------------------------------------------

void display() {
  stroke(c);
  noFill();
  ellipse(x,y,diameter,diameter);
  c = color(0);
}

//--------------------------------------------------------------------------

 boolean nearAnotherAgent(Agent b) {
   boolean near = dist(x,y,b.x,b.y) <= diameter;
    for (int i = 0; i < ag.length; i++) {
   if (near) {
       nearAgent[i] = b;
   }
   else {
     nearAgent[i] = null;
   }
   }
   return near;
 
 }
}

Ok I wasn't sure about that. So, I needed a double loop to check one with another - that makes sense. All is working fine now. Thank you once again!