how to check if photon crossed a boundary in tissue in matlab

main.m
% Load tissue properties volume, assuming it's a 3D matrix with voxel values
% representing the absorption coefficient and scattering coefficient
load('tissue_properties.mat'); 

% Photon position and direction at current time step
position = [x,y,z];
direction = [dx,dy,dz];

% Convert position to voxel indices
indices = round(position ./ voxelSize);

% Calculate distance to next voxel boundary
% (Assuming voxelSize is the same for all voxels)
deltaDist = voxelSize ./ abs(direction);

% Move photon to next voxel boundary
position = position + deltaDist .* direction;

% Convert position to voxel indices
nextIndices = round(position ./ voxelSize);

% Check if current and next voxels have different tissue properties
if tissueProperties(indices(1), indices(2), indices(3)) ~= ...
   tissueProperties(nextIndices(1), nextIndices(2), nextIndices(3))
    % Photon crossed a boundary in tissue
end
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