Hi there, i have just recently taken up processing and this is my first attempt at any code - which i obviously have a problem with. Apologees if this is a daft question?

The code below simply creates some agents with a random heading which move forward ahead-left, ahead or ahead-right. An agent is a line of two points, current xy and next xy.

I seems to work ok, other than they revert back to standard origin, after i set them up at centre. I know that can't pass data from setup to draw so how could i fix this please?

Thanks for any help.

the code:

Ant [] army = new Ant [300];

void setup() {
 size(300,300);
 smooth();
 for (int i = 0; i < army.length; i++) {
 army[i] = new Ant();
 }
}

void draw() {
 background(255);
 for (int i = 0; i < army.length; i++) {
   army[i].heading(army);
   army[i].draw();
 }
}

class Ant {
 PVector position;
 PVector heading;
 int [][] coordinates = { {0,1}, {1,1}, {1,0}, {1,-1}, {0,-1}, {-1,-1}, {-1,0}, {-1,1} };  
 int dir;  

 Ant() {
   position = new PVector(width/2,height/2); //initialise at centre
   float a = random(8);
   int b = int(a);
   //ensure elements of same 1Darray,  
   heading = new PVector(coordinates[b][0], coordinates[b][1]);
   translate(position.x,position.y);
   line(0,0,heading.x,heading.y);
 }

 void heading(Ant [] army) {
   //set heading
   float a = random(-2, 2); //generate random number -1, 0 or 1
   int b = int(a); //generated number defines heading
   dir = (dir + b);    
   if (dir == -1) {int(dir = 7);} //loop around
   if (dir == 8) {int(dir = 0);}
   // constrain to screen:
   heading.x = (heading.x + width) % width;
   heading.y = (heading.y + width) % width;
 }
 
 void draw() {
   //draw a line, current xy to next xy
   position = heading.get();
   //current xy becomes previous next xy
   heading = new PVector(position.x+coordinates[dir][0],  position.y+coordinates[dir][1]); //new next xy
   line(position.x,position.y,heading.x,heading.y);
 }
}

the setup position is 0,0, which i translate to centre of window
but immediatly after when they start to move they jump to standard origin; 0,0 in the top left hand corner.

I want them to move out from the centre.

thanks

Thanks PhiLho,

forgive me if i'm being a total noob here but i thought the problem is that in setup i translate the starting position (origin of 0,0) to the centre of the window.

then in draw i make the currentXY the previous nextXY - and as the nextXY is one of coordinates (which is an array of moores neighbourhood, being 0,1; 1,0 etc) it causes the agent to jump to the top-left corner of window, as this is the standard origin. After this the programme works fine - so i think its that having translated the origin in setup to the centre it is jumping back to standard topleft corner.

how can i stop it jumping back - i really hope i'm not misisng the point in your last mail, apols if so - just trying to understand. Thankyou for any help.

best.

OK, quick hack to show the idea:
Code:

class Ant {
 PVector position;
 PVector heading;
 int [][] coordinates = { {0,1}, {1,1}, {1,0}, {1,-1}, {0,-1}, {-1,-1}, {-1,0}, {-1,1} };  
 int dir;  

 Ant() {
   float a = random(8);
   int b = int(a);
   //ensure elements of same 1Darray,  
   heading = new PVector(coordinates[b][0], coordinates[b][1]);
 }

 void heading(Ant [] army) {
   //set heading
   float a = random(-2, 2); //generate random number -1, 0 or 1
   int b = int(a); //generated number defines heading
   dir = (dir + b);    
   if (dir == -1) {int(dir = 7);} //loop around
   if (dir == 8) {int(dir = 0);}
   // constrain to screen:
   heading.x = heading.x % width;
   heading.y = heading.y % width;
 }
 
 void draw() {
   //draw a line, current xy to next xy
   position = heading.get();
   //current xy becomes previous next xy
   heading.x = position.x+coordinates[dir][0];
   heading.y = position.y+coordinates[dir][1]; //new next xy
   pushMatrix();
   translate(width/2, height/2); //move to centre
   line(position.x,position.y,heading.x,heading.y);
   popMatrix();
 }
}