diff options
Diffstat (limited to 'face_beam_interaction.m')
| -rw-r--r-- | face_beam_interaction.m | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/face_beam_interaction.m b/face_beam_interaction.m new file mode 100644 index 0000000..4294c11 --- /dev/null +++ b/face_beam_interaction.m @@ -0,0 +1,107 @@ +function [is_face_hit, hit_position, hit_distance, new_beams] = face_beam_interaction(beam, faces) + %% calculates refracted and reflected beam after interaction with a face + % beam - structure defining the light beam + % beam.origin - array [x,y] origin/soutce of the light beam + % beam.k - k vector i.e. direction [kx,ky] + % beam.intensity - intensity of the beam + % beam.face - if ibeam starts from face then its index is here + % faces cell array of face structures + % face - structure definiong the beam + % face.vertex1 - [x,y] of the 1st point/vertex of the face + % face.vertex2 - [x,y] of the 2nd point/vertex of the face + % face.n_left - index of refraction on the left hand side + % with respect to 1st -> 2nd vertex direction + % face.n_right - index of refraction on the right hand side + + + k=beam.k; + + %% we go over all faces to find the closest which beam hits + Nfaces=size(faces)(2); + hit_distance=Inf; + is_face_hit = false; + hit_position = [NA, NA]; + closest_face_index=NA; + for i=1:Nfaces + if ( beam.face == i) continue; end + face=faces{i}; + [hit_distance_tmp, hit_position_tmp, is_face_hit_tmp] = beam2face_distance(beam,face); + if ( hit_distance_tmp < hit_distance ) + % this is the closer face + is_face_hit=is_face_hit_tmp; + hit_position=hit_position_tmp; + hit_distance=hit_distance_tmp; + closest_face_index=i; + end + end + + if (!is_face_hit) + new_beams={}; + return; + end + + %% closest face + face=faces{closest_face_index}; + kf=face.vertex2 - face.vertex1; % not a unit vector + + hold on; + % draw face + t=linspace(0,1); + x=face.vertex1(1)+kf(1)*t; + y=face.vertex1(2)+kf(2)*t; + plot(x,y,'k-'); + t=linspace(0,hit_distance); + % draw beam + x=beam.origin(1)+k(1)*t; + y=beam.origin(2)+k(2)*t; + plot(x,y,'r-'); + + % find is beam arriving from left or right. I will use vectors cross product property. + % if z component of the product 'k x kf' is positive then beam arrives from the left + if ( ( k(1)*kf(2)-k(2)*kf(1) ) > 0 ) + % beam coming from the left + n1=face.n_left; + n2=face.n_right; + else + % beam coming from the right + n1=face.n_right; + n2=face.n_left; + end + + % normal vector to the face, looks to the left of it + nf=[ kf(2), -kf(1) ] / norm(kf); + % incidence angle calculation + cos_theta_i = dot(k, nf) / (norm(k)*norm(nf)); + sin_theta_i = - ( k(1)*nf(2)-k(2)*nf(1) ) / (norm(k)*norm(nf)); + % positive angle to the right from normal before incidence to the face + theta_i = atan2(sin_theta_i, cos_theta_i); + + % reflected beam direction + theta_normal = atan2(nf(2), nf(1)); + theta_reflected = theta_normal + pi - theta_i; + + beam_reflected.origin = hit_position; + beam_reflected.k = [cos(theta_reflected), sin(theta_reflected)]; + beam_reflected.face=closest_face_index; + new_beams{1} = beam_reflected; + + + % refracted beam direction + % refracted angle with respect to normal + sin_theta_refracted_rel2normal = n1/n2*sin(theta_i); + if ( abs(sin_theta_refracted_rel2normal) >=1 ) + % total internal reflection + else + % beam refracts + theta_refracted_rel2normal = asin( sin_theta_refracted_rel2normal ); + theta_refracted = theta_normal + theta_refracted_rel2normal; + + beam_refracted.origin = hit_position; + beam_refracted.k = [cos(theta_refracted), sin(theta_refracted)]; + beam_refracted.face=closest_face_index; + new_beams{2} = beam_refracted; + end +end + + + |