Okay, it was my fault: I started it. Been pestering @garagecoder and @David_Tschumperle in PMs about summed area tables and related matters. It was also gcd’s fault for creating a traffic jam On the road to 3.0. This thread is a detour, a new road for all things SAT. Please post here, so others can follow.
The SAT is an old concept, coined in the year I was born, but used way before then. (I know many of you are way older than me: respect!) The concept doesn’t have to be limited to 1-2D either. One can generalize it to higher-dimension images; e.g., SVT (summed volume tables). You can read about SAT here: https://en.wikipedia.org/wiki/Summed-area_table.