Data densification could take place in the source if you chose to fill in missing data with certain joins, unions, or custom queries. But here, we are focused on data densification that takes place in Tableau after aggregate data is returned from the source. Specifically, under certain circumstances that we'll now consider, Tableau fills in missing values in the aggregate data in the cache, as seen in this diagram:
You'll recognize this diagram as very similar to the diagram we examined when we started the discussion on Table Calculations. In fact, data densification happens at more or less the same ...