Added some commented example code to perform convolution with FFT.

Signed-off-by: Nicola Vigano <vigano@yoda.esrf.fr>

zUtil_Deformation/Gt6DVolumeToBlobProjector.m

@@ -246,6 +246,36 @@ classdef Gt6DVolumeToBlobProjector < Gt6DVolumeProjector
 
             sino = permute(sino, [1 3 2]);
 
+%             % Example of same code, but using FFT
+%             padded_size = slice_size + sizes_shape_funcs(1:2) - 1;
+%             shifts_sf = [round((padded_size - sizes_shape_funcs(1:2)) / 2), 0];
+%
+%             padded_sino = zeros([padded_size, size(sino, 3)], 'like', sino);
+%             shifts_sino = [round((padded_size - slice_size) / 2), 0];
+%             padded_sino = gtPlaceSubVolume(padded_sino, sino, shifts_sino);
+%             padded_sino = fft2(padded_sino);
+%
+%             cumul_pos = 0;
+%             for ii_b = 1:numel(shape_funcs)
+%                 bl = shape_funcs(ii_b);
+%                 padded_intm = zeros([padded_size, bl.bbsize(3)], 'like', bl.intm);
+%                 padded_intm = gtPlaceSubVolume(padded_intm, bl.intm, shifts_sf);
+%                 padded_intm = fft2(padded_intm);
+%
+%                 temp_mult = padded_sino(:, :, ii_b * ones(shape_funcs(ii_b).bbsize(3), 1)) .* padded_intm;
+%                 temp_mult = ifft2(temp_mult);
+%                 inds_u_temp_mult = shifts_sino(1) + (1:slice_size(1));
+%                 inds_v_temp_mult = shifts_sino(2) + (1:slice_size(2));
+%                 temp_mult = temp_mult(inds_u_temp_mult, inds_v_temp_mult, :);
+%                 temp_mult = fftshift(real(temp_mult), 1);
+%                 temp_mult = fftshift(temp_mult, 2);
+%
+%                 inds_sino_sf = cumul_pos+(1:shape_funcs(ii_b).bbsize(3));
+%                 sino_sf(:, inds_sino_sf, :) = permute(temp_mult, [1 3 2]);
+%
+%                 cumul_pos = cumul_pos + shape_funcs(ii_b).bbsize(3);
+%             end
+
             cumul_pos = 0;
             for ii_b = 1:numel(shape_funcs)
                 sino_slice = sino(:, :, ii_b);