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function proj_geom_vec = astra_geom_2vec(proj_geom)
%--------------------------------------------------------------------------
% proj_geom_vec = astra_geom_2vec(proj_geom)
%
% Convert a conventional projection geometry to a corresponding vector-base
% projection geometry
%
% proj_geom: input projection geometry (parallel, fanflat, parallel3d, cone)
% proj_geom_vec: output vector-base projection geometry
%--------------------------------------------------------------------------
% This file is part of the ASTRA Toolbox
%
% Copyright: 2010-2021, imec Vision Lab, University of Antwerp
% 2014-2021, CWI, Amsterdam
% License: Open Source under GPLv3
% Contact: astra@astra-toolbox.com
% Website: http://www.astra-toolbox.com/
%--------------------------------------------------------------------------
% PARALLEL 2D
if strcmp(proj_geom.type,'parallel')
vectors = zeros(numel(proj_geom.ProjectionAngles), 6);
for i = 1:numel(proj_geom.ProjectionAngles)
% ray direction
vectors(i,1) = sin(proj_geom.ProjectionAngles(i));
vectors(i,2) = -cos(proj_geom.ProjectionAngles(i));
% center of detector
vectors(i,3) = 0;
vectors(i,4) = 0;
% vector from detector pixel 0 to 1
vectors(i,5) = cos(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorWidth;
vectors(i,6) = sin(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorWidth;
end
proj_geom_vec = astra_create_proj_geom('parallel_vec', proj_geom.DetectorCount, vectors);
% FANFLAT
elseif strcmp(proj_geom.type,'fanflat')
vectors = zeros(numel(proj_geom.ProjectionAngles), 6);
for i = 1:numel(proj_geom.ProjectionAngles)
% source
vectors(i,1) = sin(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginSource;
vectors(i,2) = -cos(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginSource;
% center of detector
vectors(i,3) = -sin(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginDetector;
vectors(i,4) = cos(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginDetector;
% vector from detector pixel 0 to 1
vectors(i,5) = cos(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorWidth;
vectors(i,6) = sin(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorWidth;
end
proj_geom_vec = astra_create_proj_geom('fanflat_vec', proj_geom.DetectorCount, vectors);
% CONE
elseif strcmp(proj_geom.type,'cone')
vectors = zeros(numel(proj_geom.ProjectionAngles), 12);
for i = 1:numel(proj_geom.ProjectionAngles)
% source
vectors(i,1) = sin(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginSource;
vectors(i,2) = -cos(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginSource;
vectors(i,3) = 0;
% center of detector
vectors(i,4) = -sin(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginDetector;
vectors(i,5) = cos(proj_geom.ProjectionAngles(i)) * proj_geom.DistanceOriginDetector;
vectors(i,6) = 0;
% vector from detector pixel (0,0) to (0,1)
vectors(i,7) = cos(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorSpacingX;
vectors(i,8) = sin(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorSpacingX;
vectors(i,9) = 0;
% vector from detector pixel (0,0) to (1,0)
vectors(i,10) = 0;
vectors(i,11) = 0;
vectors(i,12) = proj_geom.DetectorSpacingY;
end
proj_geom_vec = astra_create_proj_geom('cone_vec', proj_geom.DetectorRowCount, proj_geom.DetectorColCount, vectors);
% PARALLEL 3D
elseif strcmp(proj_geom.type,'parallel3d')
vectors = zeros(numel(proj_geom.ProjectionAngles), 12);
for i = 1:numel(proj_geom.ProjectionAngles)
% ray direction
vectors(i,1) = sin(proj_geom.ProjectionAngles(i));
vectors(i,2) = -cos(proj_geom.ProjectionAngles(i));
vectors(i,3) = 0;
% center of detector
vectors(i,4) = 0;
vectors(i,5) = 0;
vectors(i,6) = 0;
% vector from detector pixel (0,0) to (0,1)
vectors(i,7) = cos(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorSpacingX;
vectors(i,8) = sin(proj_geom.ProjectionAngles(i)) * proj_geom.DetectorSpacingX;
vectors(i,9) = 0;
% vector from detector pixel (0,0) to (1,0)
vectors(i,10) = 0;
vectors(i,11) = 0;
vectors(i,12) = proj_geom.DetectorSpacingY;
end
proj_geom_vec = astra_create_proj_geom('parallel3d_vec', proj_geom.DetectorRowCount, proj_geom.DetectorColCount, vectors);
else
error(['No suitable vector geometry found for type: ' proj_geom.type])
end
end
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