public Cellule positionDebutCercle (){
		int direc = this.cercle % 4;
		Coord d, c;
		do{
			switch(direc){
			case 1 : d = new Coord(distanceCercle(), 0); break;
			case 2 : d = new Coord(-distanceCercle(), 0); break;
			case 3 : d = new Coord(0, distanceCercle()); break;
			default : d = new Coord(0, -distanceCercle()); break;
			}
			c = this.forum.coord.add(d);
			if(distanceCercle() != 0)
				d.divEgale(distanceCercle());
			direc = (direc + 1) % 4;
		}while(this.env.horsLimite(c.add(d.add(d.multiple(vision / 2)))) && direc != this.cercle % 4);
		
		if(direc == this.cercle % 4){
			return null;
		}
		else{
			return this.env.getCellule(c);
		}
	}