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James Dansereau 944b28bd0d M-29: wire up opt-in N64 3-point texture filtering (BACKLOG B1 groundwork)

The sm64ex 3-point filter shader path already existed in gfx_opengl.cpp but
was never reachable from config, and its min-filter row was all GL_NEAREST
(no mip sampling) so it would shimmer badly.

- gfx_opengl.cpp: 3-point min-filter row -> GL_LINEAR_MIPMAP_{NEAREST,LINEAR}
  so minification uses the mips it already force-generates at upload;
  anisotropy default 0 -> 4 (0 was invalid for GL_TEXTURE_MAX_ANISOTROPY).
- video.c: Video.TextureFilter now accepts 2 = 3-point + trilinear.
  DEFAULT STAYS 1 (bilinear) -- 3-point is more console-authentic but
  softens textures at normal viewing distance, and (tested) did NOT fix
  the Depot roof garbage. That is a separate texture-data/UV/effect bug,
  not filtering -- BRIEF-B2 updated, next step is a GE_DTEX probe.

Verified: default (bilinear) -level_09 frame 320 unregressed vs golden
(nonclear delta 0.00pp, phash 11); build green; 1200-frame -level_30 run
crash-free with 3-point active.

2026-08-30 21:09:53 -04:00

3.9 KiB

Raw Blame History

BRIEF — B2: Depot (-level_30) wrong-colour / garbage textures

M-29 diagnostic pass. Not fixed. Evidence captured, leading hypothesis recorded. Companion: docs/BACKLOG.md B1/B2, docs/SMALL-FIXES.md C-section.

Symptom (captured)

-level_30, opening loading-bay area, GE_PCDUMP frames ~700-1150 (camera panning up toward the roof):

The ceiling / roof surface renders as bright blue with a dense green speckle and radial "light-ray" streaks emanating from a point. On N64 this is a dark, low-contrast corrugated roof.
Walls (green wall panels right, tan crates left) look approximately correct — mild green tint at most.
HUD ammo digits mirrored = D116, unrelated.

Frames: ppm/frame_0007..1150 this session (regenerate with GE_PCDUMP="700-1600:150" ./build-pc/ge007.x86_64.exe -level_30).

UPDATE (M-29, later): filtering RULED OUT

Enabling N64 3-point filtering + trilinear mips + 4x anisotropy game-wide (the B1 work, now default) did not change the Depot roof — the blue speckle + radial rays render identically at 640x480 native. So this is NOT grazing-angle aliasing. It is a real texture-data / UV / effect bug on that specific surface. The radial rays converging to a point look like either a broken texture matrix (rotating/scrolling tc), garbage UVs on the ceiling geometry, or a mis-rendered light-shaft effect (wrong blend/opacity). Needs the GE_DTEX probe below to identify what draws it.

(superseded) earlier hypothesis: grazing-angle aliasing / B1

The radial-ray + sparkle pattern is the classic grazing-angle aliasing signature of a high-frequency texture sampled with point/bilinear filtering and no working LOD/mipmap chain. The ceiling is at a very shallow angle to the camera in these frames — exactly where N64 3-point + LOD filtering suppresses shimmer and our fast3d path does not (see BACKLOG B1: "whole game has an interlaced/shimmering look"; port/fast3d/gfx_pc.cpp mip handling is stubbed — gfx_lod_tile_offset / "for now just ignore smaller mips" at ~1540, and D107 notes fast3d fabricates a crop when detail textures are off).

Decode path was audited and looks correct:

gfx_dp_load_tlut byteswaps entries (PD_BE16), palette_to_rgba32 decodes RGBA16 5551 and IA16 correctly, rdp.palette_fmt is set from other_mode_h & (3<<G_MDSFT_TEXTLUT) (line ~2389).
import_texture_rgba16 / ci4 / ci8 decode textbook-correct, BE reads.
D72 already disabled the PD normal-derived texgen for GE, so the streaks are not env-mapping.

Nothing in the decode path obviously produces "blue + green speckle".

Next diagnostic step (for a focused session)

Probe the ceiling draw: in gfx_pc.cpp import_texture / the tri setup, GE_DTEX=1-gate a log of {orig_addr, fmt, siz, palette_index, line_size_bytes, width, height, cms/cmt, other_mode_h & TEXTFILT, tex_lod} for the first ~200 unique textures on -level_30. Identify which entry is the ceiling (large, tiled, grazing).
If its fmt/siz and data look sane → confirm B1: the fix is proper trilinear + a real mip chain (or an N64 3-point-filter emulation shader), per BACKLOG B1 "MVP: one good default filtering mode". Do B1 first, then re-shoot this frame; B2 likely collapses into it.
If the data is garbage (wrong TMEM offset, wrong decompressed RZ section) → it's a real decode/addressing bug: check line_size_bytes vs full_image_line_size_bytes (the SUPPORT_CHECK at import_texture_rgba16:657 is commented out with a TODO about garbage full_image_line_size_bytes), and the RZ section offset from rzipGetSomething() in src/game/image.c.

Risk / scope

B1 (filtering + mips) is a medium fast3d task with a clear reference (PD port, Nightdive 3-point emu). It is the highest-leverage single graphics fix — addresses the game-wide shimmer complaint AND (hypothesis) most of B2. Do it as its own focused effort, not inline.

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