parallel_weighted_backproject

diffct.analytical.parallel_weighted_backproject(sinogram, ray_dir, det_origin, det_u_vec, detector_spacing, H, W, voxel_spacing=1.0)

Voxel-driven parallel-beam FBP backprojection with analytical constant.

Runs the dedicated parallel-beam FBP gather kernel (one thread per output pixel, linear interpolation of the filtered sinogram, no distance weighting because parallel beam has no source) and multiplies by 1 / (2 * pi) so a unit-density disk reconstructs to amplitude 1.

Assumes the input sinogram has already been ramp-filtered with ramp_filter_1d and weighted by angular_integration_weights.