Algorithms for spatial resampling and image blending

I am looking for some details on some basic algorithms… I understand that Pix4D is a proprietary software and that the exact algorithms used are not disclosed to the public. However, for scientific usage of data processed with Pix4D, it is important to know some details.
For example:

  1. what resampling algorithm is used when the desired GSD of the orthomosaic differs from the GSD of the input images? and
  2. how are images fused/blended in the overlapping areas? (averaged, weighted, …?)

I have looked into the whitepapers on this page:, but none of those seem to answer my questions, unfortunately.
For a start, I’d be happy to at least know the names of the algorithms (or even algorithm families) - I do not need to know details on their specific parameters.
In general, if such things are not at least roughly disclosed to the users, processing with Pix4D seems like it would no longer be an option for serious scientific purposes unfortunately.