thejayman77
ba74bbd5aa
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>
92 lines
4.0 KiB
Markdown
92 lines
4.0 KiB
Markdown
# Ch403 — authentic vertex-color modulation
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## Objective
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Make the 224139 static-frame fixture use the captured GS lighting state instead
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of drawing every texture at raw DECAL brightness. Geometry, draw order,
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runtime CLUT handling, persistent Z, and the Ch402 40-epoch staging partition
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remain unchanged.
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## Finding
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The selected draws carry `TEX0.TFX=MODULATE` and non-unity per-vertex RGB.
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Ch402 deliberately forced `TFX=DECAL` and emitted zero placeholder RGB, which
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made the composite much brighter than the PCSX2 frame.
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The first Ch403 fixture proved a second, narrower gap: the existing MODULATE
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implementation was only connected to the combined affine texture path. These
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SH3 triangles use the five-cycle perspective path, whose emit was explicitly
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hardwired to the raw texel. Consequently the live board completed every gate
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but produced a framebuffer byte-identical to Ch402.
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## Implementation
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- `tools/gs_make_sh3_scheduler_fixture.py`
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- adds opt-in `--auth-color-tfx`;
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- preserves authentic `TEX0.TFX` and per-vertex RGB;
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- interpolates RGB when clipping triangles;
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- applies the same GS `texel * vertex / 128` saturation rule in the
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independent reference.
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- `rtl/gif_gs/gs_stub.sv`
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- aligns the already-computed S2 Gouraud color with the perspective texel by
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four registers;
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- applies MODULATE at the perspective S1+5 emit;
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- shares the existing three-channel modulation datapath between affine and
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perspective paths, avoiding a duplicate multiplier set;
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- leaves DECAL output byte-identical.
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- `sim/tb/top/tb_top_psmct32_sh3_zint640_shared.sv`
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- verifies the full 64-bit staged header and committed TEX0 state;
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- fixes late-epoch diagnostic fill accounting.
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## Fixture
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`zsrt139a9` retains all 68 Ch402 draws in 40 staging-safe epochs. The largest
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list is 1844 of 2048 words (204 words headroom).
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The independent modulated reference is:
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`captures/gs/silenthill3/extracted/recon/sh3_zsrt139a9_ref.png`
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Against the PCSX2 224139 image resized to the same 640x480 comparison grid,
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the fixture-only reference improves RGB MAE from 31.34 to 23.31 and RMSE from
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45.94 to 33.61. This does not claim full fidelity: missing draws/fog and the
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perspective/XY precision deficit remain visible.
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## Verification
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- Generator preflight: 40 epochs, max 1844 words, no staging overflow.
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- Focused epoch 39 MODULATE proof:
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- old DECAL hash: `37401414dd6ee3b2888d4ddb4aff98903900475e6cf2a47d973959ee05d05fb8`
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- MODULATE hash: `c85edea3d42e983a31f630b7fffc1457c26233492c332860b7913c20ad7613c0`
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- average nonblack RGB sum: 258.49 -> 113.23; geometry remains present.
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- Focused Ch402 DECAL regression remains byte-identical at the old hash.
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- Full 40-epoch RTL:
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- 649,189 fragments fed; 332,984 passed persistent Z;
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- 40 markers, 40 rises / 39 falls, zero drops/overflows/BRESP errors;
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- Z mismatch `0/307200`; color mismatch `0/131618`;
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- framebuffer SHA-256
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`d286e9d5839fc7ab63ae6bc1aa3c26fa867397171ad3d1a5e5edc3b6c5b14964`;
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- PASS.
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- The final shared-multiplier implementation reproduces the focused MODULATE
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hash exactly and its late-epoch diagnostic passes with zero errors.
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- Owner Quartus 26.1 GUI fit:
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- setup worst slack `+0.080 ns`, TNS `0`;
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- hold passes, worst reported slack `0.000 ns`, TNS `0`;
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- 37,353 / 46,800 ALMs, 53,238 registers, 284 / 358 RAM blocks,
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4,177,064 memory bits, and 153 / 376 DSP blocks;
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- core RBF SHA-256
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`28659ebfccb19f03478fcd105904cc1b03195e8cc0907fad3903f56d7821975b`.
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- Live-board acceptance:
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- all 40 epochs completed with every texture CRC, palette checksum, staged
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word/record count, fresh-drain, fragment-drop, and bus-response gate clean;
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- host runner returned `0`;
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- the 307,200-word board framebuffer compares byte-for-byte with RTL;
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- board and RTL framebuffer SHA-256
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`d286e9d5839fc7ab63ae6bc1aa3c26fa867397171ad3d1a5e5edc3b6c5b14964`.
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## Status
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Complete and accepted on silicon. The current HDMI image is the authentic
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vertex-color-modulated 40-epoch composite; the next fidelity work is geometry
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precision and remaining GS effects/draw coverage, not Ch403 correctness.
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