%% Initial test and plot of the model

%%	model - structure describing the 2D rectangular model. 
%%		The structure should contain the following fields:
%%		model.xz0  - array of (x,z) coordinates of the upper-left corner
%%		model.dxz  - array of (dx,dz) increments in the grid (cell dimensions)
%%		model.nx and model.nz - numbers of grid cells 

model.xz0 = [0.0, 0.0];

model.dxz = [20.0, 20.0];

model.nx = 10;
model.nz = 10;

model.ncells = model.nx*model.nz;	% total number if model parameters

src = [ 0, 70 ];
%src = [ 0, 100 ];
src = [ 0, 80 ];
src = [ 30, 10 ];	% test source position

rec = [ 200, 20 ];
%rec = [ 200, 100 ];
rec = [ 200, 40 ];
rec = [ 200, 150 ];	% test receiver

% The following shows how you can trace an arbitarry ray.
% Note that by dropping the semicolon ';' at the end of this line, you can view
% the contents of matrix 'ray' As any other Matlab variable). 
% Each column contains information about a cell crossed by this ray,
% as explained in the description of function 'trace_ray()'

ray = trace_ray(model,src,rec);

% Note that in matrix L, the ray is represented by a row containing the ray-segment lengths 
% within each model cell. This row can be easily obtained like this:

rowL = zeros(1,model.ncells);		% first, initialize with zeros
rowL(1,ray(1,:)) = ray(2,:);		% put segment lengths into columns corresponding to cells 

% plot the model and ray 
% ===================================================================

figure(1)
clf
set(gca,'Ydir','reverse')

plot_model(model)

plot([src(1),rec(1)],[src(2),rec(2)],'g-')	% original ray

plot(ray(3,:),ray(4,:),'bo')		% entry points into cells

plot(ray(5,:),ray(6,:),'r+')		% exit points from cells

ray

% print the expected ray length and the sum of its segments
 
ray_length = distance(src,rec) 

sum_segments = sum(ray(2,:),2)