%   [D,S] = perform_front_propagation_2d(W,start_points,end_points,nb_iter_max,H);
%
%   'D' is a 2D array containing the value of the distance function to seed.
%	'S' is a 2D array containing the state of each point : 
%		-1 : dead, distance have been computed.
%		 0 : open, distance is being computed but not set.
%		 1 : far, distance not already computed.
%	'W' is the weight matrix (inverse of the speed).
%	'start_points' is a 2 x num_start_points matrix where k is the number of starting points.
%	'H' is an heuristic (distance that remains to goal). This is a 2D matrix.
%   
%   Copyright (c) 2004 Gabriel Peyr