mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-27 10:38:46 -04:00
Matthew Stanley
60 lines
3.5 KiB
Markdown
60 lines
3.5 KiB
Markdown
# Native-wide projection correction
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Trusted title plugins can call
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`psx_mod_set_native_wide_projection_correction(1)` to recover horizontally
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saturated GTE vertices during native-wide rendering. The default is disabled.
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It is independent of the user-facing geometry and perspective-texture options.
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The PS1 clamps projected screen X to -1024 through 1023. Two different vertices
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can therefore collapse onto one X edge, folding a planar quad when a wider view
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reveals its triangles. The renderer recovers the original horizontal projection
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from the existing PGXP transport only when the packet address and complete word
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match, depth is present, the integer Y still agrees, and X actually extends past
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the corresponding saturation edge. Missing or stale provenance stays stock.
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The bounded projection transport's own +/-4096 endpoints are rejected.
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This changes host triangle positions only. Guest SXY registers, packet words,
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vertical coordinates, NCLIP, collision and ordering-table behavior stay intact.
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With zero native-wide reveal, including a selected 4:3 view, correction is
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inactive. Existing geometry correction can still supply subpixel coordinates
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for ordinary vertices when the user enables it separately.
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`ws_nw projection_correction=0|1` provides a diagnostic A/B toggle. The reply
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reports the selected policy and the cumulative corrected vertex count, reset
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on a policy change. It does not toggle geometry or texture correction.
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The executable GPU regression uses a captured folding GT4 shape, verifies both
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triangle windings after recovery, and checks unchanged packet/Y data, both
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saturation edges, zero reveal, disabling the policy, missing depth, stale words,
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wrong addresses and transport endpoints. The PGXP regression separately verifies
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that a saturated MFC2/store retains its exact extended projection while the
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ordinary conservative geometry consumer continues to reject it.
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This policy cannot recover a projection whose provenance has already been lost
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through unsupported CPU arithmetic, or repair a guest culling decision made
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before GPU submission. Those paths still need title-specific qualification.
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## Saturation-aware winding consumers
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A title can separately bind exact branch words with
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`psx_mod_set_native_wide_nclip_sites(addresses, expected, count)` and list its
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BLEZ, BGTZ or BGEZ consumers under `[widescreen.cull] nclip_exact_sites`.
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Enable `[widescreen] precise_nclip = true` to collect checked GTE projections.
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No sites are bound by default. Architectural NCLIP MAC0 and FLAG remain stock;
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only the selected rendering branch consumes the corrected winding.
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This narrower predicate requires a matching native MAC0, live projection
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generation, matching packed words and integer Y, positive depth outside the
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GTE near region, bounded precision coordinates, and an X projection that
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exceeds its corresponding saturation rail. It leaves ordinary subpixel winding
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unchanged. Zero reveal, stale/missing precision, altered branch words, other
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addresses, speculative execution and timeline invalidation retain the native
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decision. Both triangle rejection and the quad's winding keep branches need
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to be identified from the title's renderer.
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Generated functions, cached overlay callbacks and the interpreter use the same
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full-word-bound host predicate. Overlay callback ABI v27 and codegen version 14
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prevent older cached modules from hiding the new forwarding surface.
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The `ws_nw` diagnostic also reports `nclip_rescues`, the number of branch
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decisions corrected since the title last bound its sites.
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