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finished reviewing normalize_v3s4 for now

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ed
2026-08-14 03:45:34 -04:00
parent 3a4d6304dd
commit b695056b9a
8 changed files with 226 additions and 103 deletions
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code/duffle/gte.h
+12 -4
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@@ -473,16 +473,24 @@ enum { _C2_TX_SUBS_ = 0
/* GPF — General-purpose Interpolation.
* PSX-SPX `geometrytransformationenginegte.md` §"GPF":
* [MAC1,MAC2,MAC3] = (([IR1,IR2,IR3] * IR0) + [MAC1,MAC2,MAC3]) SAR (sf*12)
* [MAC1,MAC2,MAC3] = (([IR1,IR2,IR3] * IR0) + [MAC1,MAC2,MAC3]) SAR (sf * 12)
* [IR1,IR2,IR3] = [MAC1,MAC2,MAC3]
* Sourced verbatim from libgte msc02 VectorNormal disassembly at 0x8001613c:
* 0x4B90003D = gte_cmd_base | gte_cmdw_gpf_compat | enc_gte_cmd(0x3D)
* bit 19 sf=0
* bit 10 lm=0
* bits 5-0 cmd=0x3D=GPF
* bit 19 sf = 0
* bit 10 lm = 0
* bits 5-0 cmd = 0x3D = GPF
* bits 24-20 = 0x19 (libgte "nonsense SDK command number" signature) */
#define gte_cmdw_gpf (gte_cmd_base | enc_gte_cmd(gte_cmd_gpf) | gte_cmdw_gpf_fake_sig)
/* Mask to round LZCR (leading-zero/ones count, range 1..32 per PSX-SPX cop2r31)
* down to even. The normalize_v3s4 half-shift logic computes (31 - LZCR) >> 1;
* clearing bit 0 ensures the subtraction result is always odd,
* so the >> 1 division is consistent (no 0.5 loss). */
enum {
gte_lzcr_even_mask = 0xFFFE, /* all bits except bit 0 */
};
#define gte_cmdw_rotate_translate_perspective_single gte_cmdw_rtps
#define gte_cmdw_rotate_translate_perspective_triple gte_cmdw_rtpt
/* RGA(Lengyel): RTPS/RTPT consume the matrix expansion of a rigid transformation (rotation matrix + translation vector) loaded into the RT/TR control registers.