`lightmaps_of_face` refactor

[snake-biscuits]

Currently id_software.quake & valve.source rely on a .lightmaps_of_face branch method
That branch method is stuck parsing a single lump
But lightmap texels can come from multiple sources

I want to be able to select a lump to pull lightmaps from in the lightmaps module
Would be really cool to be able to compare different lightmaps visually
Gotta do this refactor to do that.

Lighting lumps

• bspx
  • DECOUPLED_LM (includes uv map?)
  • LIGHTING_DIR
  • LIGHTING_E5BGR9
  • LMSTYLE16
  • RBGLIGHTING (headerless .lit)
• id_software.quake
  • LIGHTING
• valve.source
  • LIGHTING
  • LIGHTING_HDR

Also .lit

struct rgb24 { uint8_t r, g, b; };

struct LitFile {
    char      magic[4];  // 'QLIT'
    uint32_t  version;   // 0x01
    rgb24     texels[];  // as many texels as .bsp, but 24-bit
};

[snake-biscuits]

I'm pretty confident in my reverse engineering of .lit
All assumed from looking at start.lit with xxd:

13:01 bikkie:~/.../Mod/Quake/maps $ xxd -c 31 -g 4 -l 8 start.lit; xxd -c 30 -g 3 -l 300 -s 8 start.lit
00000000: 514c4954 01000000                                                      QLIT....
00000008: 393838 585757 6a6969 727171 5f5e5e 525151 4a4949 000000 5a5959 5e5d5d  988XWWjiirqq_^^RQQJII...ZYY^]]
00000026: 605f5f 585757 4d4c4c 424141 000000 5b5a5a 5b5a5a 565555 4e4d4d 464545  `__XWWMLLBAA...[ZZ[ZZVUUNMMFEE
00000044: 3e3d3d 000000 000000 000000 1e1717 271d1d 342424 402d2d 4a3636 514141  >==............'..4$$@--J66QAA
00000062: 544f4f 5b5a5a 6b6a6a 363535 1c1a1a 242020 2f2a2a 383332 433c3c 4d4848  TOO[ZZkjj655...$  /**832C<<MHH
00000080: 575555 696868 6d6c6c 363535 1c1b1b 232222 2c2b2b 363535 403f3f 4b4a4a  WUUihhmll655...#"",++655@??KJJ
0000009e: 585757 6a6969 727171 4b4a4a 000000 000000 3f3f3e 40403f 424241 414140  XWWjiirqqKJJ......??>@@?BBAAA@
000000bc: 3f3f3e 464645 474646 494848 494948 454544 4e4d4d 515050 555554 535352  ??>FFEGFFIHHIIHEEDNMMQPPUUTSSR
000000da: 4e4d4d 555554 5b5b5a 60605f 5e5d5d 565555 585757 605f5f 686867 656564  NMMUUT[[Z``_^]]VUUXWW`__hhgeed
000000f8: 5b5a5a 575656 5e5d5d 656564 626261 595958 525251 565655 5b5a5a 595958  [ZZWVV^]]eedbbaYYXRRQVVU[ZZYYX
00000116: 525251 4a4a49 4c4c4b 4f4e4e 4e4e4d 494948 424141 424141 444443 444443  RRQJJILLKONNNNMIIHBAABAADDCDDC

laid out it's pretty clear that after QLIT 0x01 it's all 24-bit texels (fairly desaturated)
comparing the .lit filesize against the LIGHTING lump size seems to confirm the theory