Why use intensity transform in sa_da

[xuwentai]

Thank you for your excellent work.I am interested in sa_ Da is quite interested and would like to study it carefully. I am interested in sa_ Da_ The 180 line code in the v2. py file is a bit confusing.

180                        # for intensity transform
181                        new_to_swap_points_intensity = recover_points_intensity_by_ratio(
182                            swapped_points_intensity_ratio, to_swap_points[:, -1:].max(),
183                            to_swap_points[:, -1:].min())
184                        new_swapped_points_intensity = recover_points_intensity_by_ratio(
185                            to_swap_points_intensity_ratio, swapped_points[:, -1:].max(),
186                            swapped_points[:, -1:].min())

Use the last column to_swap_points of as the strength value, but it only contains xyz. The shape of the input points is points: [num_points, 3], and it does not contain the strength value,
Can the author provide a brief explanation，thankyou.