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thejayman77 ba74bbd5aa Snapshot: fog implementation + fidelity tooling baseline (pre bilinear-clamp fix)

Per-vertex GS fog end-to-end (gs_stub emit incl. persp_emit5, gs_prim_list_feeder
XYZ2->XYZF2 on PRIM.FGE, gs_make_sh3_scheduler_fixture.py F/FGE packing), new fog
TBs, fidelity attribution tooling. Functional baseline before removing the dead
bilinear lerp8 clamps (Codex: 161-node comb loop -> -0.042ns setup fail).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-07-20 19:56:46 -04:00

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Ch426 — authentic vertex-alpha repair and atmospheric composite

Root cause

The scheduler generator's --auth-color-tfx path preserved captured RGB but called bake.rgbaq_with_q(), a legacy helper that always writes alpha 0xff. The first captured alpha fan actually uses vertex alpha 0x03 at the anchor and 0x00 at the remaining vertices. Under MODULATE+TCC, forcing that alpha to 0xff made the authentic additive blend roughly two orders of magnitude stronger and produced Ch425's white rectangles.

gs_make_sh3_scheduler_fixture.py now packs the complete captured 32-bit RGBA word when authentic color is enabled. It also fails closed if emitted RGBAQ alpha differs from the canonicalized source vertex. Legacy fixtures without authentic color retain their old opaque-alpha behavior.

Repaired fixture

zsrt139f22 regenerates the same 53 visible PSMT8 fan draws used by Ch405, in three exact-state groups, with:

captured RGBAQ alpha;
native GS 12.4 screen coordinates;
parsed kick semantics, authentic scissor, and framebuffer clipping;
authentic Z/TEST/ZMSK and ALPHA state;
runtime CLUT, MODULATE color, and production bilinear sampling.

The repaired geometry expands to 218 one-triangle bounded epochs. The final chronological candidate zsrt139f23 is Ch424's 125 epochs followed by the 20 authentic CT32 darken epochs and the 218 repaired alpha epochs: 363 total. The rejected PSMT4 pass is not included.

Production RTL acceptance

The complete replay passed:

1,009,406 fragments fed; 990,062 passed;
363 markers, zero fragment drops, zero color overflows, zero AXI errors;
Z mismatch 0/307,200 and color mismatch 0/245,314;
framebuffer SHA-256 ccf574d7e7ab06a519488c187da08b8c56dce5b923b6909dafba11cad6b4ce4a.

Against the PCSX2 frame, the accepted display mapping measures MAE 20.0713 / RMSE 28.9639, improving on Ch424's 20.9469 / 29.7626. The new image adds a soft captured atmospheric veil without the false white rectangles.

A controlled no-darken replay (zsrt139f24, Ch424 + repaired alpha) also passed exactly but measured 20.0890 / 29.0439. The chronological CT32 pass therefore provides a small measured improvement as well as preserving the captured order; zsrt139f23 remains the accepted candidate.

Silicon acceptance

No new Quartus compile was needed. The timing-clean Ch423 RBF (17d1c1b49aac4d893ed56285cf0703bf375db2ee9f472ea36862cca376ae63fe) ran all 363 epochs on the DE25. Every texture CRC, palette checksum, staged record count, ordered drain, and zero-drop gate passed; the host returned rc=0 and enabled the HDMI line-buffer source.

The board dumped all 307,200 words with 196,889 nonzero pixels, bounds (0,0)..(511,479), sum32 0xb59376d4, and xor32 0x28c61f44. Board and RTL framebuffer dumps are byte-identical and share the SHA-256 above. Ch426 is accepted on silicon and is the current live HDMI baseline.

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