ReaperOfVeriod/Going-Commando
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Locate the tie texcoord field at i16[4]/i16[5], and rule out the (6,7) artifact

Browse Source 
Scoring each adjacent i16 slot pair of the 16-byte tie vertex for 12-bit
fixedness over 36,501 level-0 vertices locates the fields:

  (i16[0], i16[1])    1.1%   not a texcoord
  (i16[2], i16[3])    4.8%   not a texcoord
  (i16[4], i16[5])   73.6%   <- the texcoords
  (i16[6], i16[7])   76.6%   <- the near-constant 4096/0 pair

(6,7) scores HIGHER and is not a texcoord. It is the near-constant 4096, 0 pair:
4096 is 1.0 in 12-bit fixed and 0 is zero, so both are trivially multiples of
4096. That is the constant artifact again -- a fixed pair would score 100%
anywhere. The field is (4,5), with (0,1) and (2,3) ruled out at 1.1% and 4.8%.

The first four slots span the full i16 range with 10,803 to 13,421 distinct values
each, so they are neither texcoords nor small fields.

The vertex base is confirmed to be vert_ofs alone. Adding the shader or control
region makes it worse --

  vert_ofs only                               73.6%
  bfc + vert_ofs                              69.8%
  bfc + control_count*control_size + vert_ofs  66.7%

-- so the 73.6% residual is not a mislocated base. Worth recording because
vert_ofs (3..7) numerically overlaps the shader region (5*shader_count, 5..20
quadwords), which made a combined base look plausible; measurement says the
simple one is right.

The test asserts (4,5) above 60% and (0,1)/(2,3) below 5%/15%, and names the
(6,7) artifact in its failure message so the higher-scoring pair cannot be
mistaken for the answer later.
This commit is contained in:
ReaperOfVeriod
2026-10-13 04:30:45 +02:00
parent 35b087c882
commit 180fc27b04
3 changed files with 110 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
docs/formats/core-data-regions.md
+22 -5
View File
@@ -1607,12 +1607,29 @@ texcoord pair to be 12-bit fixed -- both words multiples of 4,096, which is how
Sixteen wins by a factor of 1.7 over the nearest alternative, so it is the
element size.
**Observed layout**, 8 x `i16`:
**Observed layout**, 8 x `i16`. Scoring each adjacent slot pair for 12-bit
fixedness over 36,501 level-0 vertices locates the fields:
i16[0..3] 10,803 to 13,421 distinct values, spanning the full i16 range
i16[4], [5] the texcoords; both multiples of 4,096 on 82.5% of vertices
i16[6] reads 4,096 on 85.8%
i16[7] reads 0 on 84.0%
(i16[0], i16[1]) 1.1% not a texcoord
(i16[2], i16[3]) 4.8% not a texcoord
(i16[4], i16[5]) 73.6% <- the texcoords
(i16[6], i16[7]) 76.6% <- the near-constant 4096/0 pair
**`(6,7)` scores higher and is not a texcoord.** It is the near-constant
`4096, 0` pair -- `4096` is 1.0 in 12-bit fixed and `0` is zero, so *both* are
trivially multiples of 4,096. That is the constant artifact again: a fixed pair
would score 100% anywhere. The field is `(4,5)` at 73.6%, with `(0,1)` and `(2,3)`
ruled out at 1.1% and 4.8%.
The first four slots span the full `i16` range with 10,803 to 13,421 distinct
values each, so they are neither texcoords nor small fields.
**The vertex base is `vert_ofs` alone.** Adding the shader or control region to
it makes things *worse*, so the 73.6% residual is not a mislocated base:
vert_ofs only 73.6%
bfc + vert_ofs 69.8%
bfc + control_count*control_size + vert_ofs 66.7%
**Not established:** what any of the eight fields *means*, and why the texcoord
rate is 82.5% rather than 100%. The residual varies with record shape -- records