add simple check for interception

1 files changed, 13 insertions, 3 deletions

diff --git a/beam2face_distance.m b/beam2face_distance.m
index ba3d16b..4df0f49 100644
--- a/beam2face_distance.m
+++ b/beam2face_distance.m
@@ -2,10 +2,23 @@ function [hit_distance, hit_position, is_face_hit] = beam2face_distance(beam,fac
 	%% 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
+	if ( ( k(1)*kf(2)-k(2)*kf(1) ) == 0 )
+		% 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
@@ -23,9 +36,6 @@ function [hit_distance, hit_position, is_face_hit] = beam2face_distance(beam,fac
 		is_face_hit = true;
 	else
 		% beam misses the face
-		is_face_hit = false;
-		hit_position = [NA, NA];
-		hit_distance = Inf;
 		return;
 	end