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feat(physics #145): Slice 1 — Position/Frame types + LandDefs.GetBlockOffset (0x0043e630)

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Introduces the two value types (Frame, Position) that represent retail's
cell-relative position pair (acclient.h:30647/30658). Types are unused
by consumers yet — zero behavior change. Also ports LandDefs::get_block_offset
(pc:69189, @0x0043e630): world-meter offset between two named landblock ids,
the ONLY cross-cell translation primitive in retail physics. Conformance tests:
same-landblock→Zero, south-neighbour→(0,-192,0) (the exact #145 cascade cell),
east-neighbour→(+192,0,0), diagonal→(+192,+192,0). 4/4 pass; full Core suite
1522 passed / 0 failed. DatFrame alias added to 4 files that had using
DatReaderWriter.Types + using AcDream.Core.Physics in scope simultaneously.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Erik 2026-06-21 10:30:20 +02:00
parent ed32db70d7
commit 438bb681a5
8 changed files with 115 additions and 18 deletions
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28
src/AcDream.Core/Physics/LandDefs.cs
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@ -141,6 +141,34 @@ public static class LandDefs
return false;
}
/// <summary>
/// <c>LandDefs::get_block_offset</c> (pc:69189, @0x0043e630): world-meter offset
/// from <paramref name="source"/>'s landblock origin to <paramref name="dest"/>'s.
/// ZeroVector when both ids share a landblock (high words equal). The decomp's
/// <c>block_byte&lt;&lt;3</c> converts to lcoord (cell) units and the literal
/// <c>·24 m/cell</c> then nets to <c>(Δlandblock)·192 m</c> per axis. The
/// degenerate <c>arg==0</c> fallbacks are ported verbatim (dest==0 → raw source
/// id; source==0 → 0 lcoord). The ONLY cross-cell translation in retail physics:
/// a delta of two NAMED cell ids, never an accumulation against a moving center.
/// </summary>
public static Vector3 GetBlockOffset(uint source, uint dest)
{
uint srcBlock = source >> 16;
uint dstBlock = dest >> 16;
if (srcBlock == dstBlock)
return Vector3.Zero;
int srcLx, srcLy;
if (source == 0u) { srcLx = 0; srcLy = 0; }
else { srcLx = (int)((source >> 21) & 0x7f8u); srcLy = (int)((srcBlock & 0xFFu) << 3); }
int dstLx, dstLy;
if (dest == 0u) { dstLx = (int)source; dstLy = (int)source; } // retail degenerate guard
else { dstLx = (int)((dest >> 21) & 0x7f8u); dstLy = (int)((dstBlock & 0xFFu) << 3); }
return new Vector3((dstLx - srcLx) * CellLength, (dstLy - srcLy) * CellLength, 0f);
}
// Retail cell_in_range: landcell, envcell, or the block sentinel.
private static bool CellLowInRange(uint low)
=> low is (>= 1u and <= 0x40u) or (>= 0x100u and <= 0xFFFDu) or 0xFFFFu;