Hello , i been trying to calculate collisions between moving points  but using collections instead of arrays and  "for" for iterating.

Ive made this code, but i cannot figure out what am i doing wrong, the problem is that the points dont change the color when they are too near as its expected .

I made the same code without collections and it works ok.

Do anybody have an idea of what is going on?

i also cant understand why im getting 0's when im print the distance.
i solved this using this code   if (( dista < 200 ) && (dista != 0.0 ) )   , but i cannot understand why im getting 0.0's . Any idea?


thank you!

M.

Code:

import org.gicentre.processing.utils.*; 

HashGrid hashGrid; 
static final float RADIUS = 50;  // Search radius for hash grid 

void setup() 
{ 
  size(400,400); 
  smooth(); 
  noFill(); 
  hashGrid = new HashGrid(width,height,RADIUS); 

  for (int i=0; i< 23; i++) 
  { 
    hashGrid.add(new Dot(random(width),random(height) , 250, 0 )); 
  } 
} 

void draw() 
{ 
  background(255); 

  strokeWeight(2); 

  for (Iterator i=hashGrid.iterator(); i.hasNext();) 
  { 
    Dot o = (Dot)i.next(); 
    o.mueve(); 

    stroke(o.getColor() ); 
    point(o.getLocation().x, o.getLocation().y); 
  } 

  hashGrid.updateAll(); // se requiere esto cuando hay movimiento para refrescar los objetos en el hashgrid

} 

class Dot implements Locatable 
{ 
  private PVector d; 
  private color l;
  float dista;

  Dot(float x, float y , float r, float g ) 
  { 
    d = new PVector(x,y); // parece que vector siempre recibe las variables x , y , z
    l = color(250, 0, 0);

  } 

  void mueve(){
    d.x = d.x +  (random(20) - 10) * 0.1 ; 
    d.y = d.y +  (random(20) - 10) * 0.1 ;

    l  = color(250, 0, 0);

    //colision
    int count_i = 0;
    for (Iterator i=hashGrid.iterator(); i.hasNext();) 
    { 
	count_i++;
	Dot d_1 = (Dot)i.next(); 

	//point(d.getLocation().x,d.getLocation().y); 
	int count_j = count_i + 1;
	for (Iterator j=hashGrid.iterator(); j.hasNext();) 
	{ 
	  count_j++ ;
	  Dot d_2 = (Dot)j.next(); 

	  if ( count_i++ !=  count_j++){

	    dista = dist(d_1.getLocation().x , d_1.getLocation().y, d_2.getLocation().x , d_2.getLocation().y);
	    // dista = dist(d.x , d.y, d_2.getLocation().x , d_2.getLocation().y);

	    //dista = dist(d_1.getLocation().x , d_1.getLocation().y, d.x , d.y);
	    //print(" " + dista);

	    if (( dista < 200 ) && (dista != 0.0 ) ){

		d_1.l = color(0, 250, 0);
		d_2.l = color(0, 250, 0);
	    }

	    else {
		l = color(250, 0, 0);

	    }
	  }
	} 
    } 
  }

  color getColor()
  {
    return l;
  }


  PVector getLocation() 
  { 
    return d; 
  }
} 




 

I don't know what your problem is, but I'd like to point out (just in case) that for Iterators, there's no guarantee that they'll return objects in the same order, so "if ( count_i++ !=  count_j++){" could not be doing what you'd hope. You should be able to just compare d_1==d_2.

After another read, I think that you're doing your checking in the wrong place.. each and every Dot is checking every dot against every other dot.. so dot 1 is checking dot[1,2,3,4...] against dot[1,2,3,4..] and then when moving dot 2 it is comparing dot[1,2,3,4...] against dot[1,2,3,4...] etc...

Each dot should only check itself against every other dot. So you only need to iterate once, and then check:"if(nextIter = this)" (but with iter.next put into a variable etc...)

So I was right in my guessing... But if you just have an issue with a library without indicating which one or where to find it, we have difficulty to help you.
Beside, your usage of the HashGrid is inefficient, you are supposed to check distance / collision only against the nearest objects, not against the whole HashGrid content...