acd603fc76
The natural coupling in a file with a uniform grid and a list of small volumes is that the grid indexes the volumes. Tested by spatial agreement, it does not. Test 1: every u16 in a cell's 32-byte payload, tried as a section-1 index and checked for its centre lying inside the referencing cell. Every field sits at the 0.138% random-control rate. Test 2: every float triple in the payload, checked for lying inside its own cell. 0.15-0.81%, also chance. Recorded a worthless number from the same run rather than dropping it: those triples lie inside the object's BOUNDING BOX in 100.00% at five different offsets. The bbox spans the whole 500 km map so any mid-range triple passes, and overlapping windows at +0 and +4 both scoring 100% is the tell -- a real field would not survive a four-byte shift. Third time in this investigation that a containment test against something large has produced a meaningless 100%. Incidental and real: u32 slots at +0, +8 and +12 are below 0x10000 in 100% of payload records while +4/+16/+20/+24 are in 11% and +28 never, so the record has three index-shaped fields and four wide ones.