function [hit_distance, hit_position, is_face_hit] = beam2face_distance(beam,face)
	%% return  distance to face if beam hits it or infinity otherwise
	% for beams and faces structure description see face_beam_interaction.m

	% defaul returning values fot the case when beam misses the face
	is_face_hit = false;
	hit_position = [NA, NA];
	hit_distance = Inf;

	k = beam.k;
	% face direction or kf
	kf=face.vertex2 - face.vertex1; % not a unit vector

	%% simple check for intersection of two vectors 
	% if beam are parallel no intersection is possible
	% we do this via simulated cross product calculation
	angle_tolerance = 1e-15;
	if ( abs( (k(1)*kf(2)-k(2)*kf(1))/norm(k)/norm(kf) ) <= angle_tolerance )
		% beams never intercept
		return;
	end

	%% let's find the intersection of lines passing through face and light beam
	% we introduce parameters tb and tf 
	% which define distance (in arb. units) along k vectors
	% we are solving 
	% xb_o+ k_x*tb = v1_x+ kf_x*tf
	% yb_o+ k_y*tb = v1_y+ kf_y*tf
	% A*t = B
	A = [ k(1) , -kf(1); k(2), -kf(2)];
	B=  [ face.vertex1(1)-beam.origin(1); face.vertex1(2)-beam.origin(2) ];
	t = A\B; tb=t(1); tf=t(2);

	% beam intersects face only if 0<=tf<=1 and tb>=0
	if ( (0 <= tf) && (tf<=1) && tb >=0 )
		% intersection,  beam hits the face
		is_face_hit = true;
	else
		% beam misses the face
		return;
	end

	% calculating hit position
	hit_position=face.vertex1+kf*tf;
	hit_distance = tb; % distance along the light beam
end