How to save the descriptors of the points which are in the 3D point clouds?

[Shangareer]

Hi, friends. I want to save the descriptors of the points which are in the 3D point clouds to a TXT file. I find that the process of saving the coordinates of the 3D points is written in the "BASE PATH/src/BundleIO.cpp" from line 822(yours may be diffirent). So the process of saving the SIFT feature descriptors can also be written in this cpp file, I think. However, I can't find which parameters I should use to do this. Is there anyone who has done the same job or has any idea? Please give me some advice. Thanks.