%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% MCXLAB - Monte Carlo eXtreme for MATLAB/Octave by Qianqina Fang
%
% In this example, we compare SVMC algorithm against conventional VMC in a
% heterogeneous domain. (see Fig. 3(b) of [Yan2020])
%
% [Yan2020] Shijie Yan and Qianqian Fang, "Hybrid mesh and voxel based Monte
% Carlo algorithm for accurate and efficient photon transport modeling in
% complex bio-tissues," Biomed. Opt. Express 11, 6262-6270 (2020)
%
% This file is part of Monte Carlo eXtreme (MCX) URL:https://mcx.space
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clear cfg cfg_svmc;

%% common MC setup
cfg.nphoton = 1e8;
cfg.seed = randi([1 2^31 - 1], 1, 1); % random seed

% pencil beam light source
cfg.srcpos = [30.5 30.5 0];
cfg.srcdir = [0 0 1];
cfg.issrcfrom0 = 1;

% optical properties
cfg.prop = [0.0   0.0 1.0  1.0    % background (air, void)
            0.005 1.0 0.89 1.37]; % spherical inclusion

% time-domain simulation parameters
cfg.tstart = 0;
cfg.tend = 5e-9;
cfg.tstep = 5e-10;

% enable boundary reflection/refraction
cfg.isreflect = 1; % turn off boundary reflection to see matched results between VMC and SVMC

% spatial resolution
cfg.unitinmm = 1;

% output fluence
cfg.outputtype = 'fluence';

% GPU settings
cfg.gpuid = 1;
cfg.autopilot = 1;

%% prepare mcx input volume
dim = 60;
[xi, yi, zi] = ndgrid(0.25:0.5:(dim - 0.25), 0.25:0.5:(dim - 0.25), 0.25:0.5:(dim - 0.25));
dist = (xi - 30.5).^2 + (yi - 30.5).^2 + (zi - 30.5).^2;
mcxvol = zeros(size(xi));
mcxvol(dist < 625) = 1;

cfg_mcx = cfg;
cfg_mcx.vol = uint8(mcxvol);

% finer spatial resolution
cfg_mcx.unitinmm = 0.5;
cfg_mcx.srcpos = cfg_mcx.srcpos / cfg_mcx.unitinmm;

%% prepare svmc input volume
tic;
[xi, yi, zi] = ndgrid(1:dim, 1:dim, 1:dim);
dist = (xi - 30.5).^2 + (yi - 30.5).^2 + (zi - 30.5).^2;
vol2 = zeros(size(xi));
vol2(dist < 625) = 1;

addpath('../../utils');
svmcvol = mcxsvmc(vol2, 'smoothing', 1); % 1: enable gaussian smoothing 0: otherwise
fprintf('SVMC preprocessing complete, ');
toc;

cfg_svmc = cfg;
cfg_svmc.vol = uint8(svmcvol);

%% run simulations
addpath ../;
output_vmc = mcxlab(cfg_mcx);   % conventional vmc
output_svmc = mcxlab(cfg_svmc); % svmc

%% convert time-resolved fluence to CW fluence
phi_vmc = sum(output_vmc.data, 4);
phi_svmc = sum(output_svmc.data, 4);

%% compare CW fluence distributions using contour lines
[yy_svmc, zz_svmc] = ndgrid(0.5:59.5, 0.5:59.5);
[yy_vmc, zz_vmc] = ndgrid(0.25:0.5:59.75, 0.25:0.5:59.75);

figure;
clines = -10:0.5:10;
contourf(yy_svmc, zz_svmc, log10(abs(squeeze(phi_svmc(31, :, :)))), clines, 'linestyle', '-', ...
         'linecolor', 'k', 'linewidth', 2, 'DisplayName', 'SVMC');
hold on;
contour(yy_vmc, zz_vmc, log10(abs(squeeze(phi_vmc(61, :, :)))), clines, 'linestyle', '--', ...
        'linecolor', 'w', 'linewidth', 2, 'DisplayName', 'VMC');
colorbar('EastOutside');

% plot media boundaries
[xcirc, ycirc] = cylinder([25, 25], 200);
xcirc = xcirc(1, :) + 30.5;
ycirc = ycirc(1, :) + 30.5;
plot(xcirc, ycirc, '--', 'linewidth', 1.5, 'color', [.5 .5 .5], 'HandleVisibility', 'off');

% other plot settings
axis equal;
ylabel('z(mm)');
xlabel('y(mm)');
lg = legend;
set(lg, 'Color', [0.5 0.5 0.5]);
set(lg, 'box', 'on');
set(gca, 'fontsize', 15);
