Collision sits inside core_data at the offset the core index gives, behind
a 0x40-byte header that self-describes: it carries its own size and the
payload size. That pairing is the invariant -- the declared header size is
exactly 0x40 on all 27 levels and header + payload stays inside the lump.
41,481,520 payload bytes across the 19 levels that have any; 8 declare
zero length, which is present-but-empty rather than absent, so the two are
counted separately.
The cells inside the payload are not decoded. They do not walk as
fixed-stride cells, and treating faces as variable-length records stops
partway into the first cell on level 0 rather than tiling the payload. The
first cell reads as 11 verts and 33 faces under every hypothesis tried,
which is exactly the kind of agreement that looks like a result and is
not one -- three different strides all produce the same first cell and all
of them are wrong. Left open rather than committed as a guess.
ReaperOfVeriod
dc941a8eec