% Heterogeneous Propagation Medium Example
%
% This example provides a simple demonstration of using k-Wave for the
% simulation and detection of the pressure field generated by an initial
% pressure distribution within a two-dimensional heterogeneous propagation
% medium. It builds on the Homogeneous Propagation Medium Example. 
%
% author: Bradley Treeby
% date: 30th June 2009
% last update: 29th April 2017
%  
% This function is part of the k-Wave Toolbox (http://www.k-wave.org)
% Copyright (C) 2009-2017 Bradley Treeby

% This file is part of k-Wave. k-Wave is free software: you can
% redistribute it and/or modify it under the terms of the GNU Lesser
% General Public License as published by the Free Software Foundation,
% either version 3 of the License, or (at your option) any later version.
% 
% k-Wave is distributed in the hope that it will be useful, but WITHOUT ANY
% WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
% FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
% more details. 
% 
% You should have received a copy of the GNU Lesser General Public License
% along with k-Wave. If not, see <http://www.gnu.org/licenses/>. 

clearvars;

% =========================================================================
% SIMULATION
% =========================================================================

% create the computational grid
Nx = 128;           % number of grid points in the x (row) direction
Ny = 128;           % number of grid points in the y (column) direction
dx = 0.1e-3;        % grid point spacing in the x direction [m]
dy = 0.1e-3;        % grid point spacing in the y direction [m]
kgrid = kWaveGrid(Nx, dx, Ny, dy);

% define the properties of the propagation medium    
medium.sound_speed = 1500 * ones(Nx, Ny);   % [m/s]
medium.sound_speed(1:Nx/2, :) = 1800;       % [m/s]
medium.density = 1000 * ones(Nx, Ny);       % [kg/m^3]
medium.density(:, Ny/4:Ny) = 1200;          % [kg/m^3]

% create initial pressure distribution using makeDisc
disc_magnitude = 5; % [Pa]
disc_x_pos = 50;    % [grid points]
disc_y_pos = 50;    % [grid points]
disc_radius = 8;    % [grid points]
disc_1 = disc_magnitude * makeDisc(Nx, Ny, disc_x_pos, disc_y_pos, disc_radius);

disc_magnitude = 3; % [Pa]
disc_x_pos = 80;    % [grid points]
disc_y_pos = 60;    % [grid points]
disc_radius = 5;    % [grid points]
disc_2 = disc_magnitude * makeDisc(Nx, Ny, disc_x_pos, disc_y_pos, disc_radius);

source.p0 = disc_1 + disc_2;

% define a centered circular sensor
sensor_radius = 4e-3;   % [m]
num_sensor_points = 50;
sensor.mask = makeCartCircle(sensor_radius, num_sensor_points);

% run the simulation with optional inputs for plotting the simulation
% layout in addition to removing the PML from the display
sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, ...
    'PlotLayout', true, 'PlotPML', false);

% =========================================================================
% VISUALISATION
% =========================================================================

% plot the simulated sensor data
figure;
imagesc(sensor_data, [-1, 1]);
colormap(getColorMap);
ylabel('Sensor Position');
xlabel('Time Step');
colorbar;